Must haves from Wings of Valor:
1. The 1.0.7.8 patch
2. Very first add on to get is Campaign Manager and the tutorial for placing patches into the game with Campaign Manager.
3. For single player:
At SWWISA go to "members", "PatWilson" and click on WFP and then download all those WFP files.
If thats a bit complicated and you want more instant results you can go to SWWISA and then "members pages", "Rens" and download one of his vol files which will give you the new models, sounds, terrain but not add new types of aircraft, squadrons, flight models, damage models, aces.
If you don't have a glide card, I think Rens has a DD vol file.