I saw some pics of Shinkis in Diorama studio with outfits like Kimonos and Cheerleader Costumes, and stuff.

Do these come with the game or do you earn them in Battle Rondo or do you have to buy them? Or do they like include a few with each Shinki you buy?

Some of them are unlocked by gaining achievements in Battle Rondo. Most of Fubuki's gear is that way, and so ar ethe cheerleader outfits. Much of it, like the kimonos, is purchased, though.