While you're leveling up, you can use your basic commendations to buy adaptive gear from the planetary vendors, credits to buy some from the GTN, or cartel coins to get some from the cartel market. If you find adaptive gear you like the look of, use your basic commendations at the modifications vendors to keep the armorings, modifications, and enhancements updated.
Good news for your companions at 55-60: Yavin 4 has a weekly mission reward lockbox with a full set of 192 gear for a companion of your choice, which you can repeat every Tuesday. It isn't modifiable, but it all looks great imo. And you can't beat level 192 gear.