My goal with this post is not to say "this is the right way to do things" but rather to share a bit of my experience to date with SteemMonsters and possibly share with others a perspective they might not otherwise see. There are many ways to skin a cat, this is just what I've done. With that, let's begin!
The Game
First off, what is this thing? While SteemMonsters seems ubiquitous on STEEM to me, there are a lot of people who buy a starter pack and don't immediately know what to do next. This is not a how-to guide, there's plenty of those. If video is your thing, I would highly recommend the intro videos 
Those are some quick pointers about getting started, but it still doesn't answer the basic question "What is this thing?". Well, obviously it's a game. More specifically it is a collectible/trading card game. Initially, collecting and trading cards was the only playable part of the game. More recently, the ability to battle has added a crucial dimension to the ecosystem. There's more coming - a lot more. Tournaments are next on the wish list, which will bring the ability to compete for prize money. Apparently, lots of people enjoy both of those things (competition and money).
I could go on and on about what the game is, but that is also not the point of this post. To summarize the intro, SteemMonsters is:
- A significant dApp based on the STEEM blockchain
- A potentially attractive investment vehicle with a functioning economy and liquid markets
- A playable online game which is somewhat addictive
- A community of people who are for the most part knowledgeable, friendly and generous
Collecting
You've got to start somewhere, and with SteemMonsters that is the starter pack. It's $10, and it comes with a steem account if you need one along with 30 cards to start playing and to build a collection off of. For anyone looking for an easy way to introduce someone to crypto, you can't find a much better solution. While most of the early adoption has been among your fellow Steemians, the target audience for this game is the general population. I've seen more than a few people discussing giving steemmonsters starter packs as holiday gifts, which does seem like a great idea for a number of scenarios.
Once you have the starter pack, you can jump into the fray immediately. You may even win some matches, without really knowing much about how it works. If you do win a few matches, you will gain some ranking points. With the current rules when you've accumulated 100 points (pretty simple to do) you will be entitled to receive one shiny new booster pack of extra cards at the end of the season. The seasons currently last 14 days. Oh, and there are daily quests for you to use different "splinters", where you can earn a pack per day if you achieve the goal. So, do that. 14 days and you'll have at least 15 more packs, probably more if your ranking points go up a bit. That's quite a few cards that start piling up. Five cards per pack puts you at 75 new cards from the 15 packs.
I would expect that due to general impatience and/or a knack for prudent investing, many of you will also explore ways to buy more cards and jump-start the whole thing. There are two ways to go about this. You can purchase as many booster packs as you want for $2 each. The awesome thing about the booster packs is that you could stumble across something quite rare and valuable. Or not. Don't get your hopes too unreasonably high there. The back of the napkin math says you want to purchase around 1,500 packs to get one gold foil legendary card. You may get lucky, it's kind of like a lottery ticket with much better odds. Also, there isn't any losing ticket, you get 5 cards to add to your deck whether they're worth as much as a new iPhone or not.
The other avenue is to buy individual cards on the open market. There are a number of ways to go about this, since the market is based on an open protocol. SteemMonsters has a market right in the UI. SteemPeak/PeakMonsters and SteemPlus both have convenient and useful tools for purchasing SteemMonster cards. I created a market at https://battlegauntlet.com which can also provide really useful information about the state of things. I'm sure there are others, and undoubtedly more are coming.
Winning
Here is the part where I'm going to share my observations in hopes that you will find it useful. Feel free to use this or ignore it as you see fit.
Most people will not have created a third-party market for SteemMonsters cards, which is mostly what I think makes my experience at least a little different than the norm. Initially, I purchased a starter pack and around 8 booster packs, long before thinking about doing any development work. Mostly my involvement was based on @Reseller being excited about what the game could become, and it seemed like a prudent investment. I was actually kind of happy with my first packs. No gold foil, but I did manage to pull a couple of legendary cards (Spirit of the Forest and Lord of Darkness). I figured I would probably be a force to contend with, once things started popping :)
Jump forward a few months, and there's a lot going on. The SteemMonsters DEX market protocol is a great thing, enabling bots to run around buying cards and alternative front ends to trade in them too. Some people invested a lot of money buying packs in bulk, and the market became a really interesting phenomenon. The headlines were being made at the high end, with some gold foil cards selling for over $1,000 each. Since I was working on testing code for purchasing cards, a lot of my interest was in the common cards that were hanging out at the low end of the market. For quite a while, the going rate on commons was around 4 cents. Sometimes 3, sometimes two. I recall 
To make a long story a little less long, I ended up with a bunch of common alpha cards, at least by my modest standards. I didn't keep a precise count, but well over 1,000 cards. I added it up recently, and all total I've put around $250 into SteemMonsters when you add up starter packs, kickstarter, and market purchases. Not a ton of money, but it's quite a lot to spend on a game. That's where the whole picture gets a lot more interesting. If it were just a game, that would be true. Since the cards are effectively a crypto token that happens to be playable, the game is a nice side-benefit, depending on how you look at it. As an investment, it has done quite well. The "almost" accidental $250 I put in is roughly worth, conservatively, over $800 at current prices.
I don't know about you, but that's the kind of picture that I look at and think "dang, would have been smart to add a couple of zeros to that". All that is to say that it's still pretty early in the development of things. I'm not about to sell those cards at current prices, because they're likely undervalued. For people just considering jumping in now, some might be inclined to whine about people playing maxed out decks because they were early to the game. I would suggest that it is more productive and will make you happier if you look more at the opportunity and the future upside potential rather than worrying about the past. There is a ton of potential to this ecosystem, and it's really just getting started.
I'm not in the big leagues - my cards are kinda mediocre compared to the heavy hitters. One of the design goals is that this game is fun no matter where you're at. I have found that to be true, whether playing a level 1 starter pack team, or slugging it out in the higher leagues, the game is challenging and interesting.
Playing
This is already much longer than I intended, but I must at least touch on the topic that I really wanted to write about. Consider the above storytelling "background info". So you don't want to invest a ton, but want to play the game and have fun. Make some money while you're at it. You've come to the right place.
First, get the starter pack and do the daily thing. Once you've got the game somewhat figured out, you'll probably have a pretty good idea of what cards you want. If you can find them within your budget, probably buy some from the market. Summoners are particularly important (and thus also relatively more expensive). Figure out what cards you want to play, and determine what level of summoner you need to support that. A simple example from my random wanderings: once the stats on the cards came out, I really wanted to play the skeleton assassin with poison. He gets poison at level 6, so I needed a level 5 summoner. Level up the summoner first, then fill in the team behind it. Believe me, it works much better that way than getting that sweet Flesh Golem up to a level 3 so he can heal, but not being able to use it because your summoner can't handle it.
Another thing to keep in mind, especially early on and ESPECIALLY if you don't have much Steem Power/RC to work with on your account, is to try to stay somewhat balanced across the various splinters. The reason that matters is that if you want to complete the daily quests you will need to win matches with the splinter you have almost no cards in. If you do have an ample RC budget, you can just lose a bunch of matches until you get down to a level where your white team can win, but that's no fun. Knocking out the daily quests is pretty important, since that's 14 packs over the season which is almost equivalent to the reward for hitting the Diamond 1 league.
The way things are right now, it probably makes sense to make your run up for points later in the season. There are two reasons. One, the longer it goes on, the higher everyone gets. As a result, the competition will be relatively less brutal in the higher leagues, assuming people aren't leveling up their cards like crazy. That is not a perfect assumption. The first season saw quite a bit of both (meaning rating inflation AND combining/leveling cards). The second reason should be obvious from the earlier discussion, which is that the lower your level through the bulk of the season, the easier time you will have completing the daily quests.
See you on the killing fields
That's a lot more than I wanted to put in one post, and I've got lots more to share, but will have to wrap it up for now. If there is one final thought for this, I want to sincerely thank the SteemMonsters team for the excellent work that they have all done. The game is superbly fun to play, the economics are well thought out, the engineering execution and the coding are top notch. You guys (and ladies) have said that your motivation is to enhance STEEM and have fun doing it. Your actions prove the words to be true, and I'm a big fan of that approach.
And there you have it. There is a solid mechanism to earn crypto on the STEEM blockchain simply by playing a game. STEEM is about much more than just blogging, and I'm certain that there's a lot more coming.