Ya, Vangaurd marks. I don't play PvP. My rep was like 1400/1500 in rank 0. So more bounties, ok...
Just a note - vanguard marks are not PVP. Those are crucible marks. Just to explain the system a bit, there are two main factions: Vanguard and Crucible. The Vanguard vendor is your class vendor and is PVE focused. The Crucible vendor is near the guy who gave you the crucible quest and is PVP focused. I'll go over how to get marks / rep below for each.
Each faction has a basic set of equipment. The head, chest, and feet cost 65 marks each. The weapon costs 150 marks. You can earn a maximum of 100 marks each week. Up to here, the system is fairly straight forward. You do PVP for crucible rep, you do PVE for Vanguard rep/marks. Here is where it gets more complicated. There are also several sub-factions. These are factions like Dead Orbit or Future War Cult. Each of these factions have a vendor located somewhere around the city. They each sell a class item that you can wear. When you are wearing that class item, ALL your rep goes to that faction. These vendors all use Crucible marks, so I refer to them as PVP vendors. I will point out below that you actually don't need to PVP to get your weekly quota of marks. The alternative is pretty boring though. These vendors carry build specific equipment. Until you get Vanguard to level 3 (you need level 3 for the weapons), don't bother. Once you do have it at level 3, pick a reputation based on the bonuses on the gear that you want. Buy the band, and wear it around.
Now on to how to get marks.
Vanguard Marks / Rep:
The most obvious way to get these marks is via the strike matchmaking. Each run takes between 20 and 30 minutes, and at low levels you get very few marks. I honestly wouldn't bother with that if I were you until you were 24ish.
Instead, run patrols and do bounties. When doing the patrols, there are 2 ways to earn marks. The first is to complete bounties. You should probably try to do 5 each day. Bounties are generally 100 rep. It takes 2000 for a level. You can do up to 6 a day. These have the added benefit that you gain faction reputation while doing them. The second is to do public events. If you stay in the same area for a while, you can also participate in public events. You get marks, reputation, and other useful items for gold starring them. The biggest drawback is that this is a grind. It takes probably ~20 hours to get a faction to level 2. Note that you can also do the little missions even when you don't have the bounty for them. They give some rep for each that you do. I do them when I am trying to rep up.
Crucible marks / Rep:
Don't bother with pvp unless you like it. Seriously - waste of time. You gain more marks per hour by running in circles in patrol gathering materials and then trading them for marks. By material, I mean spin metal, ghost blooms, helium filaments, or relic iron. Basically, pick an area you like and run around visiting chest spawn points and material spawn points. Once you learn all the points for an area, you can generate a circle that will give you ~100-150 per hour. You get 5 marks per 50 material.
For reputation, once you have your vanguard rep to rank two, go to any of the pvp vendors and buy your class item. That item will allow the patrols and bounties to raise your rep. Basically, you repeat what you did for vanguard rep.
Other options:
Once you get to level 24 you can start running strikes for rep and marks. Run the highest level one. The reason I say wait until 24 is the level penalty you get for being below the mobs level. It can be frustrating at lower levels because just about everything one shots you. You also cannot damage bosses if you are 2 levels below the strike level.
You can also run pvp. This can be frustrating if you don't like it. It isn't well balanced right now. If you do run it, try to get yourself a good shotgun. Just find good places to hide and wait for things to come around the corner and then shoot them at point blank range. As a warning, better players know about this and won't let you do it. But there are generally enough people just running around the map that you can get a few kills.
Or - and I do not endorse this - just run around the map shooting at everything you see and trying to die a lot. It sounds bad and it is - because it will force your team to lose. However, you also force the game to end early and get marks faster. I've seen people stand and spin in circles while shooting so they can watch TV and still get marks. It is actually a bit annoying.
The weekly and daily are good mainly for coins. If you are doing the daily bounties and at least one public event, you should get enough coins and motes of light to buy items from Xur each weekend. That will get you exotic weapons.
I know you are probably doing a lot of this already. These are really the best way to do things though. It is a lot of grinding and not terribly fun.
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