METAL GEAR SOLID V: THE PHANTOM PAIN

This achievement is one you just get out of the blue typically depending on how much you focus on developing stuff.

It counts the Developed Items for yourself, your buddies, the helicopter and also base development. Personally I unlocked it just after Mission 12, but I was prioritising this achievement so I was quite low on GMP a lot of the time.

Honestly, if you want to try and rush this achievement, then i'd say go for the cheapest items to develop, but then again i'd also highly recommend just allowing it to occur whilst playing the game, cause after all I highly recommend playing it as it is pretty fun to play.