I recently was able to get one of my old gyms back by remembering the password.However I noticed the new gym features aren't on may old ones such as upgrading the styles, seeing the stats, even equipping equipment, etc.Anyone know how to fix that problem!

Screenshot what you are seeing. There was weird glitch minute ago. Make sure stat style selected, as everyone's went blank and we could not see stats.

turns out my stat sheet was off, but I still can't equip any equipment such as gloves, shorts, tattoos, to none of my fighters for some reason

If you buy them, you can. You have to buy clothing first.