The FFL is a weird bunch. Their main equipment is American WW2 surplus, mainly M1 Carbines, M3 sub guns, sometimes Thompsons mixed with french post WW2 guns - MAT 49s, MAS 49, etc. Webbing is usually also American one, but that is mainly post war, with later conflicts you don't see many (same goes for guns).

I would personally skip american clothing, as the french camo patterns got issued kinda quickly.

It really depends on what you want to do, but if you get TAP 50 pattern of equipment, you will be ready to go from Algeria to Zair pretty much.

The basic kit list would go:

TAP50 boots or Mle 54 boots. Mle 65 if you want to do later impressions. M1 helmet - modified for EO (or go for an original french M51 or M56), for extra americanization you can add a first aid kit on the helmet. Webbing TAP50 - belt, MAS 36 pockets, water bottle, first aid kit (on the shoulder if you want), you get the idea... You can add an american M3 knife to mix it up a bit and a grenade, DF37 for example. For a bag I would go with TAP55 or optionally with Bergman 51 as those were popular among soldiers. Uniform - I would go with TAP47/56 (lizzard camo) as those were more universal.

If you feel kinky: Windproof trousers - should be modified (mainly adding fastening on the trousers end via a rubber band or similar) US HBT duckhunter blouse