And the best way in my opinion is to do level 24 strikes while wearing a faction piece of class armor. you have a chance at legendary engrams and you can rank up a faction to buy legendary weapons/ armor. you will need crucible marks but those can be obtained by turning in materials to the crucible quarter master. you can keep your faction armor on while on patrol so you can do patrols and collect materials. this is what got me to level 27 I hope this helps. I got it done in a weekend so you should be able to do it if you are willing to spend the time.