What’s the most efficient way to level up?
The best way to get from Level 1 - 20 is to play the campaign. The end of the campaign takes you to level 20.
After the campaign, the most ‘efficient’ way to level up are public events, but adventures and crucible will get you acquainted with the game better
Once your power level is in the 260s: the Rare-engram climb will slow down. Focus on planetary vendor tokens (Devrim, etc.) to obtain Legendary engrams. This is also a good time to do exotic weapon quests.
After 270+: Milestones (Nightfall, weekly Crucible quest, weekly Public Event quest, etc.), exotic weapon quests, exotic engrams, raid, Trials of the Nine.
TL;DR:
- Level 1-20 - campaign
- Power level up to low 260s: Public Events/Adventures/Crucible
- Low 260s: exotic weapon quests, planetary vendor tokens
- 265+ - Luminous Engrams via milestones, exotic weapon quests, exotic engrams, raid, Trials of the Nine.
What do I do with my uncommon/rare gear?
In early game, you can continue equipping gear that raises your power level until you can get legendaries. Once you get legendaries (purple), you can infuse any rare gear into them to raise the power level of that gear.
As a side note, save five rare (blue) or higher scout rifles for an exotic weapon quest down the line.
Do I decrypt my engram immediately or wait?
Engrams decrypt at the level they drop, so there’s no reason to hoard them - go to the cryptarch and have fun! The exception are luminous engrams - those are rewarded as powerful rewards and can boost your power level significantly. It’s probably best to unlock those once you’re 260+