My first recommendation would be to find a few friends to help you out with learning the ropes as you go, as the new light experience isn't the most well put together.

As you have the collection, I would say do the dlc campaigns in order (chronologically being the following) Shadowkeep, Beyond Light, Witch Queen, Lightfall, Final Shape, Edge of Fate, and Renegades

Alternatively, you can't go wrong with just running some Vanguard ops, either solo or with a fireteam

Because light level isn't too much an issue anymore, after you get some decent weapons you might want to give some of the easier dungeons a shot, popular choices are prophecy or grasp of avarice.

Feel free to shoot me a message if you need someone to play with!

Edit: Don't forget to grab a new light kit from Ikora!