The only raid you can do is VOG normal and that's only on your level 26. You can't do nightfall or Crota's End with any of your characters until they are at least a level 27. Even at level 30 you will have to be carried because you will have little to no affect on the enemies. My suggestion would be go grind a ton of bounties and strikes, buy some vanguard gear and get yourself to a level 28/29 and then you can jump into these event and carry your own weight.