I'm trying to do this now, and I find it hard to keep geared. The options I know of for gear are these: Get if from PvE monster drops, get it from PvE mission rewards, take the PvE comm rewards and buy it that way, buy the sub-50 "pvp" gear using PvP comms, buy it from GTN, pass it down from your own higher level toons ( or I suppose get some other nice person on the fleet to give it to you.
I haven't been using a higher level toon, but I think I'm going to have to. For everything except the weapons, the PvP gear from coms only comes in lvl 20 and lvl 40 flavors, which would leave you a severely undergeared lvl 39 if that's all you did. And I find that I don't make enough credits from strickly PvP matches to be able to afford to keep geared off of GTN.
But maybe I'm missing something.