A new feature in 2022 is GEAR.   Your avatar (created legend) can now equip gear obtained from Event rewards or Mystery Boxes and include: Headwear, Tops, Bottoms,  Shoes,  Gloves,  Eyewear and Bats .

From the Team menu, select My Legend > Gear

   

Tap the "i" for Information in the upper left of the gear screen.

You may upgrade an item with GEAR XP:

If you wish to trade in a piece of gear for Gear XP, UNEQUIP the item and tap "Trade Shop,"  

Select the item (it will outline in green) and tap "Trade Item."