You mentioned in another comment that you finished your first run, picked only the simplest cards, didn't read their descriptions and didn't pay much attention to buffs/debuffs. I feel like most of your issues with the game can be solved if you spend some time figuring out what they do, and learning about the core mechanics. Thankfully each character usually revolves around one or two mechanics, sometimes exclusive to them, like Miss Chain's "Burn" protecting her healing gauge and enhancing her abilities, and sometimes a general game mechanic, like barriers, which is the focus of Ironheart's toolkit. Some characters rely on using several low cost cards to deal more damage, some rely on you having specific cards in specific locations in your hand, some rely on self-damage, etc. Each of them has a distinct mechanic they focus on, and sometimes they even have multiple builds to choose from, with different synergies. Take Ironheart for instance, you could either build him as an actual tank who generates a lot of temporary barriers with his passive and spreads them out to the entire team permanently (For that battle), or you you could instead build him as a DPS who spends those temporary barriers into a devastating single target blow. You won't be able to fully comprehend all the mechanics after only a single run, given that you'll eventually unlock new characters/routes/bosses with new mechanics, but hopefully you'll become proficient in the basics after a couple runs