These are the fastest means of leveling up in Destiny 2. There are other methods such as Public Events and Story Missions, but these methods take a very long time – much more than just running around and killing stuff.
The best way to speed level is by finding a Lost Sector  , and repeating it over and over, giving you Legendary Engram drops on each boss completion. One such location is the Widow’s Walk Lost Sector, in the EDZ, one of the original areas of Destiny 2.
The second fastest way to level up is by doing Public Events and Strikes.
Some players disagree with this method as it takes roughly twice as long as just running Lost Sectors over and over.
To run Lost Sectors, simply find one on your map and head there. In the case of Widow’s Walk, all you have to do is go straight from where you spawn in, past two large barriers, and it’ll be at the end of the path.
Enter the door to encounter three enemies with a yellow bar above their head. This is a Patrol-type event, and you just need to kill all the enemies in order for it to count. You will get a Legendary Engram drop for killing each enemy.
Repeat this process over and over again until the boss spawns, which appears after about three waves of enemies. In the case of Widow’s Walk, you’ll find it at the end of the path, before the two large barriers. He gives you a loot chest upon killing him.
It is suggested that you make sure to use an Auto Rifle for these types of events (preferably one with Solar damage), as they do bonus damage against yellow bar enemies, which are almost always yellow bar enemies.
It is also suggested to use Kinetic weapons for the other types of Lost Sector bosses, so that you don’t waste ammo on hitting their shield.
After defeating the boss, simply restart the event and you’ll be able to go straight back in there – you won’t be kicked out when your Fireteam leaves or goes into other areas.
This means you don’t have to go through the door again, as long as the boss is not dead yet. In other words, if one or two enemies are remaining and there’s a big yellow bar over their head, you can still go in there without being kicked out.
It should be noted that this technique does NOT work for Escalation Protocol, as the game will kick you out upon moving to another area.
You do not need to run Heroic Public Events (the ones that trigger at the end of a normal one) in order to get Legendary Engrams – that only gives Radiant Shards and Upgrade Materials. You can still play Public Events on their default difficult (Normal) to get Legendary Engrams as well as other loot.
A good way to make sure you don’t die is to have one player with a build specifically designed for support, such as this Sunbreaker Titan Support build .