I dont exactly know what to do..

I am not 18 which means I cant open a coinbase, (binance, etc.) account. I do, however, have a custodial account opened with my parents and I was thinking about investing in a crypto etf. Although I did see many issues with these etfs actually tracking the performance of its respective currency. They also tend to have high expense ratios. Would it be wise to just invest in one for now or just wait until I turn 18?