I wouldn't worry about one unless your really into PVP. IF you are then I guess one of the PVP ones. Personally I wouldn't waste the marks/honor for one at that level though.
You really won't see many for quite a while. I was level 49 before I saw my first one(the old insignia of the alliance, the 5 min cooldown one). Level 52 before I ended up getting my Carrot.
Unless you're a Jewelcrafter, an engineer, or an Alchemist, I wouldn't expect to see anything other than a trinket from PvP(the Insignia and the AB one, iirc) until you're at least in the 40s.