Sell unwanted items for XP from the Armory
Special edition weapons; (enlisted, professional, elite) and equipment which you build up can actually be sold. Go over to the weapon and hit the square button on Playstation or the x button on Xbox. You’ll see that you can redeem the item for XP. You can get up to 2000xp per item.
Next, is your classes and loadouts. When you setup your classes, all the weapons and killstreaks have challenges and completing the challenges will give you bonus xp. Tip, look for attachments that you can unlock easily such as “Get 20 kills while aiming down the sights…”