No real order to what you should be doing - just run HVTs (high value targets) assignments, search and destroy missions, and daily's.
What system are you playing on?
I'm on PS4. I'm just so, so rusty. I need to ease myself into things before I try anything too taxing. Will my gear score be high enough to take on dailies etc...? I don't mind matchmaking for stuff as that was half the fun during my initial play-time last year.