Just like everyone else said, the bounties you do only gives reputation The little circle thing on the top left when you go to a quartermaster or mentor guy whatever :P since you're level 20 I believe you can do the strikes that rewards 2 marks per completion, so there's a good starting point. Public events rewards 4 I think. So just google "destiny public events" and there should be a website that tells you where a public event MAY occur. But continue doing bounties because that's one of the easiest ways to level up the guy that gives you legendary gear in exchange for marks. Keep up the good work bruh