Start running the vault of glass for gear that will get you to 29/30. Once you get to L29 u can run hard VoG for some of the best primaries in the game.

Why don't u just buy armour from the vanguard or crucible rep?

Basically, keep doing the highest level strikes you can do for engrams, daily mission for engrams if you can. I'm not sure at what levels are needed for both of those to reward you with engrams. Do the weekly strike for coins even at its lowest level. Save enough and buy something from Xur when it's available. Keep doing strikes from the playlists like I said before to get vanguard commendations There's also crucible commendations from pvp, you need a faction specific class item to level up the different factions in pvp if you want any of their gear. But there is a default vendor as well for crucible. Try to do one public event at least per day for the daily reward from those do a google search for destiny public event and you should easily find a website that gives you a rough time for when each area has an event starting. Once you reach level 26 you are at the bare minimum for the vault of glass raid and can see if people will take you. As well, if you have the expansion the new story missions and strike do reward you with items for first time completion as well as the quest lines that Eris has. She has a gun and gloves you can get. Also, if you keep doing bounties you will eventually be offered 3 different exotic bounties that if you complete one of them you get an exotic weapon. I think you need level 24-26 for the expansion.

Most of the above comments are great, only thing I would add is plan ahead. I was in the same situation as you are for a while, then I figured out how to use the system to your advantage. Buy the legendary gear, figure out what you want to do (auto, scout, hc, ect) and plan around that with the armor attributes. BUT, those can only take so much experience before they are maxed and you are waiting on shards. Now go buy more legendary boots and gauntlets. Have them equipped when you dump off your bounties.. You do not need to even spend the glimmer to upgrade anything on them, but once they are maxed out via experience dismantle them. This should give you about 6 shards per piece that you can then throw at the gear you actually want to use. Tada level 28 or 29 if one is exotic. Good luck!

You can acquire enough gear to get to level 29 in two to four weeks, starting from scratch. Earn your maximum vanguard marks each week (100), buy your first piece of 65 Mark gear first week, left with 35 marks. Buy the second and third piece of 65 Mark gear on week two, left with 5 marks. At this point it is best to use strange coins or motes of light and buy an exotic helm from Xur, but otherwise you need to spend two weeks getting marks to purchase a helm for 120 marks. Upgrade that gear, and you have level 29. I recommend only going to 27 and then raiding on normal to replace everything but the exotic helm, this will be enough to take you to 30, at which point you want to raid on hard if you want the raid helmet.