Honestly... Depending on what you are doing... Just make sure your weapon is optimal rank, then for everything else... find stuff in the mid-low 20 range.

Yeah optimal rank gear will be "best" because you'll get the full value for every stat... but there are so many pieces of gear out there that you could be carrying a bunch of crap just to rank from 16 to 21 (which can be done in one sitting depending on how much you like grinding.)

The stat differences from the level 16 thing you are optimal for and the 22 thing you aren't optimal for are pretty small. and the convenience of not having to buy and carry a bunch of gear that you will use for a short period of time more than makes up for the few stats you are missing out on.

Unfortunately, a lot of this game is amorphous right now.

Between the changes we can't see and the changes that are so small as to barely have an effect... just go with stuff that looks good until about 25... then start looking for the optimal rank gear upgrades.