Start running level 20 vanguard strikes. Earn vanguard marks and rep. Buy legendary armor from your vanguard mentor. You're welcome Edit: forgot to mention...complete ALL the vanguard bounties every day first thing, before you start running strikes. Fastest way to gain rep and level your weapons. Also, as you level up your blue armor, your light level will rise. Try and play strikes that are at your level or 1 above. You get more marks from the higher level strikes.