How should I be gearing?

This is my first time playing WoW Retail (dabbled some in classic) but played a few other MMOs. Me and my friend were wanting to do Heroic dungeons, but needed the right item level. My luck was kind of bad during delves/world events and rares and kept getting gear that was higher Ilvl than my current one, but would take away stats that my class needed (fire mage)

I decided to take a hit once in a while just to reach ilvl for Heroics and managed to still be able to clear them and do my job, but wanted to know if that was the right call, or if there was another way I wasnt aware of?

I know about the champion gear from renown and I already have 1 and working on another right now.