You have to keep collection apparel items in sponsor boxes until you get enough points for the next upgrade level. The higher ones take more time as you need progressively more points. The best way is to just play the coin games with sponsors turned on. If you want to play more than just the free sponsor times then you will have to spend credits to unlock them but IMHO it’s a waste of credits. Same with buying Apparel points or sponsor boxes in the ProShop.
No matter which route you take it will take time and you will need to be patient.