Among the many prizes found in Japanese Game Centers, it’s not surprising to find a few things you can wear.
The most common wearables are t-shirts, usually marked as “free size” (read: too small for me). Much less common are caps/hats and hooded blankets/towels. There was a short period a few years back when light jackets showed up in machines, while the current popular wearable seems to be slippers — though none of these could be considered common, either.
The N.E.E.T. brand is the best source for clothing items: I’ve seen t-shirts, hooded sweatshirts, sweat shorts, sweat pants, and caps (plus long wallets and several types of backpacks/duffel bags for accessories).
Even less common items are brand-specific one-offs: Inu×Boku SS clip-on tails, Rilakkuma socks, Dark Souls-style helmets, Terra Formars plastic masks, Attack on Titan fabric masks, Ika Musume squid caps, and Hatsune Miku-style hair accessories.
The last kind of wearables seem designed with clubgoers in mind. Everything is an accessory, and everything lights up: fingertip lasers, shoelaces, horns, earbud cords, and even t-shirts.
You may not be able to amass a full wardrobe with the (incomplete) list above, but much of it is of surprisingly good quality; the KanColle scarf I got last year is wider and warmer than either of the ones I brought with me, my Persona 4 Kuma slippers keep my feet warm here as well as they did back in America, and I wear my Evangelion tie to work one week a month (and my Ika Musume messenger bag every day). Otaku fashion is the best fashion.