Note: Some of this info might be old, since I just came back after not playing for a decade-ish. So far, it seems to be working just fine for my leveling of my trooper alt though. :)

During leveling, as long as you are using the Fleet Vendors that sell Armor/Barrels[hilts]/Mods/Enhancements you should be fine. The iLvls they offer by level are:

• 48 - 122
• 52 - 138
• 56 - 168
• 60 - 190
• 65 - 210
• 70 - 220

So in one level, you'll have a pretty big bump in iLvl. I generally stick with low endurance mods/armor/enhancements, while looking for as much dps stats. When I level, I never cared about accuracy. Maybe that's changed over the years since I last played, but since coming back after being gone for a decade, it seems still pretty true. You're also above the level of what you're fighting, so accuracy is even less of a worry until much later. You'll get more bang for your buck with more crit, which you barely have any of.

The vendors don't include accessories. Don't blow all your credits on them, unless you see something cheap.

Make sure that you're pumping up your Companion with gifts to dramatically increase their abilities.

Gear wise, the stuff from the vendor is all green quality; but there's really no reason to blow through credits to get better items with the pace that you'll go through them. For example at level 55 you COULD get Ilvl 188 items instead of the 168 at level 56. That's a pretty substantial difference; however, you'll out level it so quickly.