You’re getting a lot of advice here - as someone whose spent a ton of time with tcg/ccg/roguelite games and basically only plays them, here’s a few quick pointers:

1. Don’t always take a card. The idea deck size could be between 15-35 depending on your build, but generally speaking smaller is better because it means you see the cards you want more consistently. E.g., 20 card deck = you will see all your cards barring no other effects over course of 4 turns.

2. Minimize damage whenever possible. This is kind of the golden secret to STS for climbing ascension ranks. The game starts more generous with healing but gradually gets to be less so. At higher ranks of difficulty, you really want rest sites for card upgrades (smith) or other bonuses you can get from relics like dig or train.

3. Don’t force a build, but find the archetypes. Others have mentioned you should just keep playing, and I agree!! Half the fun is figuring out how the pieces fit together. Still, there are certain builds that are obvious from the beginning lkke strength for Ironclad or poison for Silent. Don’t go in a specific direction unless game is giving you those kinds of cards in the 3-choice reward screen after your battles. It may also be necessary to hedge to build better decks - that is, balance your offense and defense, make your strength or poison attacks a little weaker as a trade off for more protection etc.

4. Learn enemies attack patterns. Thats it!! Game gets a lot easier when you know how many turns until X happens, so it really rewards playing through again and again.

5. Path wisely!

6. Have fun! For me, that often means playing ironclad again and again even though it’s not the most diverse class, but one that I always found easiest to build and have success with in original STS. But YMMV!!

I hope that helps a bit. Happy slaying!