I've been messing around for awhile now but can't seem to equip anything and when I open my inventory it shows that it is empty but when I go to my Moghouse or to a vendor to sell, I have my weapon and ring and the coupon I can't seem to get rid of. Is it a glitch on my side?

you change equipment under the Equipment menu.

You can’t sell the coupon and you can’t sell equipped gear. you also can’t move equipped gear between different inventories - have to unequip first.

depending on what city you started in, you can trade the coupon to an npc to get 50 gil