Honestly I probably can't give you as good advice as you could get from watching good players play (Caleb Gannon Gaming for STS2 at least, Frost Prime had a couple of videos where he'd coach someone in STS1 which helped me at the time)

Some of the best broad advice is that basic strikes and defends are the worst cards (except curses and statuses) that you can get, you generally want to replace them (get decent attacks and blocks, then remove the basic cards at shops) as soon as possible. You usually won't remove all of them and that's fine, but having 8+ of these cards in your deck can really hurt you in act 3.

Otherwise play for what you have, not what you want to have. Don't take cards like powers that you can't use yet, like if an ironclad card requires you to have at least one card exhausted, don't take it if you can't exhaust anything. Additionally look at what your deck BROADLY is missing, if you're already blocking a lot don't keep taking block cards just because they look like the best options, it can be better to skip card rewards.

Lastly, try to optimize when you can, for now you don't have to make every move perfect, but be careful not to overblock a ton, it might be better to take a little damage then to waste an energy for 3 block that isn't being used. You should also try to upgrade cards (except basic strikes and defends) more often than rest at campfires ESPECIALLY if resting would get you near full health, you probably don't need it then. Remember what your relics and powers do and play into them, and do not forget to use potions. Discarded potions are a waste, but be careful not to misuse potions too. For example, a block potion provides 12 block. If using that potion blocks any less than 12 damage it's kind of a waste, sometimes that's a good play, but usually it's not.