As stated in the Splatoon Direct, gear will be more than fashionable, they will be functional. Gear will increase your basic stats, as well as give you certain abilities. The gear’s ability to hold these boosters will depend on their Star Count. Each piece of gear can hold up to four abilities (three star gear). After the first ability, each ability gained will be assigned at random. In order to gain more abilities, you must play with that gear multiple times to level them up.
Another way to increase the amount of ability slots your gear has is to visit Spyke. If you don’t like the abilities you were assigned, Spyke can reroll the abilities your gear possesses. Each of these services will cost you a Super Sea Snail.
You can get gear in multiple ways. Each piece of clothing has it’s own shop: Jelonzo runs Jelly Fresh, the tops (shirt) shop, Crusty Sean (the Tiger-Prawn) runs the shoe shop, Shrimp Kicks, and Annie and Moe (Anemone, in case you missed that pun) run Cooler Heads, the headgear shop. Finally, a horseshoe crab by the name of Sheldon runs a Weapon Shop, Ammo Knights. Here is where you can new gear as you unlock it throughout the game.
So what if you see someone else wearing cool gear? If you take a closer look at them (much as you do the miis in the Mii Plaza, you can special order whatever gear they are wearing at the time. You can then go pick up this order through Spyke.
Splatoon will release globally on May 29th, 2015.