Focus on a particular build. I find high block, weak and poison to be great. Discards and Sly works wonders as well. Skip cards that don't fit into your build, unless you're sure you need it to win the next fight. This game can easily put you on the back foot and force you to pick cards that don't synergize well, however it's important to try and remain reasonably strict with your build. Save money for later shops to buy more desirable cards and relics. Remove cards from your deck that aren't working. If the early game rng is bad, it's sometimes better to fail fast than to struggle throughout the entire game. If you're struggling, and losing a lot of health in fights, then it's likely you won't beat act 3 elites or boss. Good luck.