Do bounties and strikes to level up vanguard and earn marks and two commendations. Buy vanguard vendor gear. Hope you get a piece or two from engrams you'll get from strikes. Or if PvP is your thing go that route, but you'll get a lot more rewards from strikes. Should be 31 in 2-3 weeks. And get someone to carry you through weekly if you can't get to a high enough level by the end if the week because there is a pretty good chance of getting a purple engram. You should get enough blue stuff to hit 24-25 pretty quick, so you might not really need a carry.