Honkai: Star Rail

It take depends on the character's role. DPS characters, for example, will shoot for crit rate or damage on body: which one is better depends on the character (e.g. Yanqing probably doesn't want crit rate). For boots, ATK is often preferred over SPD, because if the DPS is faster than your supports, you may run out of skill points. For the rope, energy regen is usually best because it's the only possible source, but ATK is fine too.

I think you're on the right track! I also try to get one that match their damage type or Res reduction for SW and stuff

You should read the character's skill, ultimate, talent, etc. descriptions to see which stat that particular ability scales off of.

For example, March 7th's skill and talent scale off of her def, so you care about that stat.

Check these sites for builds. They list preferred main and substats for each character and slot.

Prydwen - Mobile Meta