MGS V quick way to get weapons?

I previously platinum'd this game and now am returning to it for fun. I remember it took ages to get decent weapons - even by the time I platinum'd it, there were lots of cool stuff still locked... that was 200 hours of play!

I usually never return to games after finishing them/platinuming them, but this game is too good - and since I am only playing for fun this time around, is there any tips or DLC or other ways to get heavy duty weapons and fun stuff faster?