We were all beginners once. I personally level up to 20 first by beating all the stories on the moon and earth. Then I go back to the first mission on the moon and farm experience from it because it has pikes. You can simply start the mission do the first couple objectives but then instead of going to the hive fortress, hope on a pike and play as if it's a patrol. Just drive around everywhere killing as much as possible. It's easier because the pike will deal damage your unable to at the lower levels. Then I go back and finish the stories to earn xp for my gear and weapons. EDIT: I forgot to mention doing as many bounties as possible YOUR QUESTION: For the gear and stuff I personally save up marks and buy it from the vanguard, then buy exotic gear from Xur. Max all that gear out and this alone will allow you to get to level 29 (almost positive, otherwise it leaves you a point or two away). From there though you are now high enough to run the tiger strikes with ease, and the raid as well. Hope this helps.