Hi Chris
If your planning to join up forget buying any kit you will be issued everything you need and I prommise you it will get ruined during basic training.
After that then you get the kit you want, ie. jetboil or crusader cookers instaed of the issue hexi burners.
As for stuff for airsoft its down to personal choice of what type of load out you want, ebay is the best place but beware cheap copy's
Other than issue kit(which is tough stuff and battle proven). I use Blackhawk and disciple kit,I have used this in the field and it has stood up to the riggors of mud, dust and crap.
If your looking at assault vests etc find somewhere to try them on before buying.
I have to use my Osprey Mkiv kit and I do miss my '95 dpm webbing but that is my choice.
Any other questions I will be glad to help