Let's say you just started playing Splinterlands. You've already spent $10 on the summoners spellbook and you haven't really found a consistent strategy for winning a ton of ranked battles (this was the case for me when I first started playing). You may not want to throw a bunch of money in on legendary cards yet until you first develop a go-to strategy. Have no fear! There is a way to develop a solid winning strategy that will consistently work at the lower level leagues for very cheap (only $3.00).
You will need to buy the Venari Wavesmith card. This card has 3 health, one magic attack and it has the ability to grant all fellow monsters with 2 armor. Buy this card on either https://monstermarket.io/ or https://www.cardauctionz.com/ to get cashback in DEC (see previous post). The huge advantage with this card is the +2 in armor. Normally early-level magic monsters don't have a lot of health so they die off quickly before they can inflict a lot of damage. But the ability of venari wavesmith will negate that. Now, for all your battles, you should choose the water splinter and select the "Arlic Summoner" in order to increase all your magic attack by +1. And now proceed to stack your lineup with magic monsters (including the venari wavesmith). All your monsters will now have a high magic attack plus they will be able to take a little damage. With the high magic attack, you will not have to worry about opponents with high speed or high armor, because magic attacks ignore both speed and armor.
If you have enough mana, make sure to add a tank at the begining of your lineup. My prefered tank early is the "spineback turtle" because it is relatively cheap in mana and it has a high health. Then stack the rest of your lineup with magic cards. Keep the venari wavesmith towards the middle-back of your lineup. If you keep it in the front and it dies early, then all your monsters will lose their armor. Conversly, you don't want to keep it all the way in the back, because it will be vulnerable to sneak attacks. So I prefer to hide it in the second from the back position. If you have enough mana, add the water summoner all the way in the back in order to negate enemies with a sneak attack.
Granted, this strategy will only work early on. As you advance to other leagues, opponenets will arrise that have counter strategies to the one I just presented.
However, this should be a good strategy to get you started.
Good luck!