I'm only at 46 wins and I've gotten 6 EXs from gym boxes, as well as another EX and EX cube from the normal dailies
this gym has been really good to me, but I don't know if I'll have time to get 100 wins for the 2 cubes
https://www.timeanddate.com/countdown/generic?iso=20170412T0459&p0=4429&msg=End+of+Pok%C3%A9mon+Duel+Fire+Gym+Cup&font=cursive