the level 20 and 40 "pvp" gear you can get from the pvp vendor isnt really pvp gear at all
there is no expertise on the gear
if you plan to pvp at 50 you should be converting your warzone comms to ranked comms trying to get max so when you ding 50 you can more quickly gear your toon
i'm not telling you not to buy the 40 "pvp" gear -- in fact, i did it on my first toon but i regretted it for a couple weeks as i had no comms when i dinged 50 and had to spend more time getting pwnd than i might have
this is just kind of a fyi post
And if you max out on comms buy pvp medpacks and adrenals. Don't waste comms on stuff, you'll need them at 50, Using them when you are under 50 is a waste.