Get your vanguard rep up by doing patrols and strikes. Patrols offer higher rep per hour. I like to do patrols while waiting for public events and I use this image (http://m.imgur.com/V7uXKGq) so I know where I have to be. Also do bounties when you have them as they offer high rep as rewards. Once you're rank two you can use your marks to buy vanguard legendary pieces.