Child Support, need to be change, in the case of the custodian, need to be audit, how they are using the Child Support

At this moment, the court, says, 'The best interest of the child' but when I ask, how the custodian is spending the child money! the court says, is not of your business is 'her' money!... I don't see is 'the best interest of the child', when my children ask me for BASIC stuffs, saying 'I asked my mom, and she said, ask your dad because I DON'T have money!!' well and the Child Support? Now I bought all my children school supplies, cloth, shoes, and the court says those are gifts????
So my petition is to change the Child Support law, where the court can demand audits to the custodian and REALLY be the BEST INTEREST OF THE CHILD... where the Court demands the custodian do prof of the investment of the child the child support.