Aside from when you get higher levels of power (the 50,000~70,000 range), you need to do a lot of calculations to ensure you are getting the best price for clothing. It would be ideal to wait for the Konoha Gift Shop and Treasure of the Sage events, which usually have Wild West and Ceremonial Kimono fragments on sale for about 50 coupons, compared to the current 75 in the normal shop (they used to be 100 coupons). Trust me, math and financing will be your best friends when it comes to buying clothing or anything in this game.