With the nerfapalooza going on, I'd suggest sticking to either the Scout Rifle or Hand Cannon weapon classes (pulse rifle too if you can find one with very high stability). General weapon power is going to shift greatly in the coming months, so don't worry about DPS and just stick with what you like. Scout Rifle is the longest range primary, but it tends to suffer with mobs of enemies. Hand Cannon has a lower reload speed and range, but it shreds enemies at mid-range or closer. It'll also give you enough practice that you'll be less likely to miss with the GG. Once you reach lvl 20, look at the different gear the factions have. Each faction's armor tends to give buffs to the same weapon types, so you'll want to have a plan for your build. Also, don't worry about getting the Vanguard/Crucible sparrows. They're hardly faster than the uncommon one you get from the story or gold chests on Earth. Bounties are the fastest way to level up, so do your best to do all the Vanguard ones each day. You can do the Crucible ones, but those tend to take longer. And if you think you'll be going for 30, do your best to get an exotic helm. That gets rid of the need for the Raid helm which can only be found on hard mode (lvl 30 enemies).