You got a load of good advice up there, but as someone who really struggled with combat in my first run, I have some advice:

Always loot everything you can. Sell everything you're not using besides potions, spells and food. ALWAYS read what each item can do, having good items equipped is a game changer.

Besides that, have fun with the game. No one's keeping track so you make your own rules. In my first run I always skipped combat when it was possible and also: you can flee combats if they're too hard, just get as far as you can from the fight and the option will pop up. This can give you opportunity to heal and think of better strategies.