Currently the lower levels of Splinterlands is filled with a lot of Water/Magic played by new players and bots. Its a very efficient way to grind rating if you dont own many stronger cards yet and it can be frustrating to play against.
Here is what I find the best, most fun and cheapest way to counter Water/Magic.
These are the main 3 ways I go. Only one of them is completely FTP so lets start with that one.
Earth/Lyanna 
Here I set it up as if we have 26 mana, but basically you can remove cards from the back the less mana you have. This is a very strong counter to Water/Magic if both sides have acces to only starter cards and it is the truely FTP way to go.
Water/Magic 
First of all my second option is NOT FTP and uses either one or both of the following cards:
KELP INITIATE - Older reward card that is a 2 mana "meat shield" here but is used in higher levels of play for the "clense" ability it gets at level 3. It cost around $10.7 at the time of writing.
VENARI WAVESMITH - Strong new reward card that gives your whole team 2 armor. This is a huge asset in all the games where we are playing against all the other splinters. It cost around $2.3 at the time of writing.
Personally I have both and mix and match them depending on what the opponent have played lately. If the opponent also have either one or both of these cards this is turning into a game of rock paper siccors really fast and going back to option 1 and playing Lyanna can be strong, unless your opponent also diverge from Water/Magic.... And down the rabbithole we go.
Water/AntiMagic
The AntiMagic lineup is basically just 2 cards:
BORTUS - The other water summoner from the starterpack that gives your opponents lineup minus 1 magic.
TORHILO THE FROZEN - Your anti magic tank that can solo some lineups with his void combined with your summoners power. It cost around $17.9 at the time of writing.
When you combine BORTUS with TORHILO all the starter magic lineups gets defubbed back down to 1 magic dmg and they then hit cratures with void for 0. This is the fun way of doing it but again not FTP.
I would not recommend trying to solo with just one creature, but put in a back line that can deal some damage just in case we were wrong about our opponent.
Im sure some will think that option 2 and 3 are a waste of time, starterset already gave us the counter lets use that. The thing is that as you get more rating and move up and meet players with a small collection things will start to change.
A card like DJINN OSHANNUS from the new rewards set is getting more and more commond to counter every day as more of them hit circulation and option 1 is getting weaker while option 2 is just losing when we meet a DJINN. This is where option 3 (AntiMagic) shines. If DJINN OSHANNUS is the only damagedealer your opponent have that can actually hit your tank (as he start out with 2 magic dmg) we will still win most of the games (again your opponent can diverge or have other stronger cards)
Finally I think this game is about progressing and the game gets more fun as you move up in ranks for me at least.
Im just a beginner my self but I hope some people will find this usefull, and that my English is not too terrible as its not my first language.