Probably best to start with the story missions, and also keep doing bounties to get your vendor reputation ranked up so you can buy Light 36 armor with Marks. It depends if you like PvE and/or PvP. Once you level up a bit more you could start doing raids (Lv26 for Normal Vault of Glass, Lv30 for Hard VoG and Normal Crota's End, Lv32 for Hard Crota's End) and hopefully get some armor drops there. Once you hit Lv30+ you could do a Nightfall especially if someone around here is able to help. If you have strange coins you could also buy an exotic armor piece from Xur who is available until 5am EST Sunday. If you need coins you could do the Weekly Heroic strike.
Anyway, hope this helps. There's so much stuff you can do sometimes it's hard to give advice for these types of questions, haha.
Thanks for your input!