i recomend you start a bank that people can put CP in and only be able to use it at your shop and cant withdraw any (mainly for me) and for every 100 they deposit at a time they get 5 extra in there bank and you could also have a few tourneys that the prize money goes straight to there bank then all the CP in the bank you could use as prize money for tourneys and other stuff
(i have lost a total of 350 CP) (each time regaining a little bit more but still)