Strikes from vanguard playlist are good for marks until you get higher level. Dailies are good for XP and ascendant materials. Weeklies are for strange coins to buy exotics from Xur. You'll want 13 for armor which you need first to level up and 17-23 for weapons. A second character of the same class passing armor through vault speeds things immensely. When you get to 29 (or 27-28 if you have really good friends willing to carry you) then you want Nightfall for a *chance* at an exotic drop and a pretty massive XP buff that lasts until weekly reset (Tuesday 4am EST). Lots of people available to help run Nightfall on Tuesday since that gets the most out of your buff. Also when you get to level 27, some folks may help you through the first 2 parts of Crota raid for a chance at level 32 armor. When you hit 28, you can start the Venus raid on normal and at 30 on hard. Best weapons still only drop from Venus raid on hard mode exclusively. For now, get vanguard marks and buy level 31 armor from vendors. Vanguard and Future War Cult are my favorite.