Clothing gives you about 500 power for the cost of 2500 coupons (kimono and wild west), a little more expensive for summer youth sai. So theres ratio 1power for 5cp. Count yourself if at your current charm/battle armor/refine/mangatama/anything level you have better options, if yes then leave clothing until nothing else is cheaper. How to count that? remove 1 mangatama/rune of a stat you want to calculate, see how much power x of that stat gives you. Remember that clothing applies to whole team, same as tactics.