What kind of equalizer is it. Built into head unit, or separate. 2 band, 3 band, 5-10, 15-30? Graphic or parametric? Nobody could even begin give you an idea of where to start without this info except to say be sparing with the boosts, try to cut what's obscuring what you want to hear more often than you boost what you're missing, and don't overboost.
I have never used loudness on any head unit. You can if you want to, but back off on your gain and/or go easy on volume.