I suggest save up cps for a month and spends on lucky board. If you want power try to go after myoboku gifts as much as you can. Last mission box event you got 100 for free. They are relatively cheap for the amount of power you get. I also suggest going after charms also and save up a to at least 250 for the rebates 500 if you want the free lvl 5 rainbow magatama. Get thread from sa and monthly event also a good place to get med refines. Costumes are decent source of power but can be costly I recommend going after anbu or summer break first. Basically save everything you get until a rebate.