This for the Splinterlands Community Engagement Challenge ( Click Here ).
We all have limited ressources. Well, most of us, there are some whales that just make more SPS on staking in a minute than one does in a whole day - including battles :-D
How to start?
Let's say you're starting out. Of course, you don't want to buy useless cards, but you also don't want to spend all your money. What shall you focus on?
Know your strategy. Do some test games via challenge with ghostcards, in the level you want. You can find battle-willing people at the SBT-Community by
- here's there discord: Splinter Battle Token Community. When you know more or less how you want to play, you can go on.
Summoners - the base of each deck. Without summoners, you can't really compete.
Neutral cards - they're almost always available, except for one particular ruleset (Taking Sides). They're also a little more expensive due to that fact.
Dragon - you can combine dragon with every other splinter, plus neutral.
Other people's collections - You can either ask the big dogs in Discord, or just look at their recent battles and which cards they used. That only gives you an idea though, since most of them play in the Champions-League :-D Still, they can give you tips on the best cards to start with.
Identify the best cards
Check out card reviews and utility lists, like the one provided by 
You can use the columns to select which league you want to compete in, and which format. For example, since you're new, you sort the first column for Modern - Bronze will be first due to A-Z anyway. You can see that Uraeus at lvl 2 (4 BCX) has a high score.
Building a plan
Make your own Excel Sheet - at least I did that. I selected all the cards that I wanted. I made a GOAT list with mixed splinters, and then a list for each splinter.
I personally started with Water, but I think Life is actually the cheapest one to start with.
Here's a picture of what my "Let's get to Gold!"-Excel for Life looks like. Those are not all the cards that I use in Life splinter, but the ones that I didn't have on Gold level yet. The green ones are already done. As you can see, I also added a column for the BCX I already own, the BCX that are my goal, and the BCX I still need. With that and the price per BCX, I can calculate the amount of money I still need to have the deck where I want it.
Example: At the current price, I would need to spend $18,48 to get Evelyn Auvera to the level that I would like to have her. That's expensive. I rather get the Grandmaster Rathe first for $5,01, since he's a summoner and so much more useful at this point.
Also: I set the price for the Reflector at $0.005 (or 5 credits) - I will not buy it when the price is above that. Things like that keep you disciplined with the money.
I did not rank them by the utility score, but rather used my experience on how often I use them, and the abilities they get at which level. I also change my mind quite a bit, and sometimes don't buy even though the card reaches my favorite price.
Find the right price
Where to observe
My favorite tool is Splintertrends (click here) by 
You can use many filters to find out what's the best deal, or just search for the cards on your list.
EDIT! comment from the creator of Splintertrends: "Be careful with average prices, because price pumps can skyrocket them in the short term. I always search for cards with 🔥 icons to find the best deals. Good hunting!😊"
High Value Cards
Prices in Splinterlands fluctuate a lot, and if you want to get the biggest bang for your buck, you have too be patient. I waited 4 months in order to get Rage at 13$/BCX and get him to level 2 - a good investment both for the game (he won me so many battles it's inconceivable), but also moneywise - he's worth 30$/BCX at the moment. So, especially with the high value cards, play it cool. Analyze them. Use the Ghost-Card function in challenges to explore them, have the right tactic before you buy them - you don't want to waste that much money on something you won't use afterwards!
Low Value Cards
There are a lot of Chaos Legion cards below 0,01$ - the cheapest are to find around 0,004$ actually. Some of those are actually not that useful, but others are. Again, research them with your favorite scoring mechanism to find out which are useful. Sometimes a good hint is also when you lose against them - I became aware of many of the cheaper cards after I lost a battle against a superior tactic with inferior cards. Splinterlands is a strategy game!
Time to Buy! (Careful, it can be addictive.)
What next? The fun - buying! I use MonsterCards as a tool to buy, since it's easy to filter and get the right cards, and I also get a bit of DEC back. The information provided by that market is very neat and detailed, and that makes it easier to get the price right. Here's the link (it's a referral): Monster Cards
Tip: If you buy with credits, you can use the fluctuation of DEC in your favor, since all cards are priced in DEC. So, if the DEC Token price falls, the cards become cheaper in credits since those are pegged (1000 Credit = $1.00). So, when you see a slump in the DEC price, check for cards that you alway wanted ;-)
There are many other pages as well Peakmonsters, the Ingame Market, and so on. You can find the one that suits you best and gives you the best info, but in the end it comes down to have made your research on the cards, knowing your strategy in battles and having lost enough battles to painfully realize what works and what doesn't - learn from your mistakes, and learn from other peoples' mistakes as well.
Thanks for sticking with me!
Oh my, that was a long text. I hope it helps someone. It actually did help me to clarify a few things in my strategy, and to get my excel sheet in order. Any comments are welcome, as always! This is how I do it, but I'm pretty sure that there are better ways to build your collection - if you know of one, please let me know!