Real simple, go with vanguard, why, they take vanguard marks, you earn those doing strikes, daily's and such forth, lot faster to earn than crucible marks, at lvl 2, you can buy armor, that armor will have 33 light, 4 pieces of that and you're lvl 31, also, save some coins, do the weekly heroic strikes, enough coins and you can buy an exotic armor piece, and bam, that's 36 light. get one or two more levels and then find a raid group to get you through crota on normal. Heck if you're on xbox one, I'd be willing to do the lamps for you, you'd have about a 50% chance of getting a piece of raid gear, thats 36 light right there and free, it'd take me a minute or two.