In Destiny you will have a few factions you can choose to help out for various rewards. Some factions have weapons and armor you can buy while others have emblems or material exchanges you can use. Check out this faction list and choose which one you want to max first!
You can buy the PVP faction bands at level 20 from the faction vendor in the tower.
Vanguard: The Vanguard faction is basically where you get your legendary class armor. All of the best armor is level 20 so you won’t be able to get it until then. In order to raise your rep with the Vanguard you will have to do bounty missions and patrol missions on the planets surface.
Crypto-Archeology: This is the faction that will help you find out what your unidentified items are. Every time you turn on in your reputation will go up. If you have extra glimmer you can buy items from him for additional rep as well. Once I made it to rank 3 they sent me a reward for possible epic loot.
The Crucible: This is the main PVP faction in Destiny. You can find them down the steps in the tower right before the Vanguard faction. The more you PVP bounties you do the more your rep will go up. They have high end armor and weapons for those who dedicate themselves to PVP.
Dead Orbit: Another PVP faction in The Tower then you can gain rep for. You will need to have a Dead Orbit cloak, mark or bond on your character in order to gain rep for them. They have high powered weapons and armor for the higher rep levels.
Future War Cult: A third PVP faction in The Tower you can gain rep for. Same as above you will need something from the Future War cult on your character in order to gain rep for the faction.
New Monarchy: Yet another PVP Faction in The Tower you can gain rep for. Wear something of the New Monarchy Faction and go complete Crucible bounties to get rep for this faction.
The Speaker: This isn’t a faction you earn rep for but he sells some high level class items. Basically once you get to level 20 you keep gaining extra experience that turns into Motes of Light that you can exchange for rare class items here. He is in the north tower past the New Monarchy.
Agent Of the Nine: This is the guy you turn your strange coins in at. He is only around on the weekends but he has some amazing weapons and upgrades. Once I find out where he is located in the tower I will add it.
When I find more I will be sure to add them to this list. Check back soon for updates!