Dude welcome to a most awesome game.
The way I approached oxps was to take it in steps.
First load up on Ambiance expansions (better looking planets, some big npc cruise ships, a new HUD, new sounds and fancy looking ship and station textures).
Then play for a while, getting familiar with the environment.
Then I added system flavour oxps, so "Anarchies" oxp for anarchy systems, Commies oxp for communist system, dictators and the excellent Feudal oxp.
This made my Ooniverse look good and seem more alive.
After that I just got on with the game for another while, now I'm making credits and my ship is getting tougher I'm slowly adding missions.
On the wiki you can arrange the mission list by galaxy and kill requirements, so you can get a nice handful of starter missions like Long Way Around and Tionisla Reporter.
Oh, actually don't forget the
most essential oxp, no point in getting any others until you've got this installed.
http://wiki.alioth.net/index.php/Beer_Cooler