Puzzled

hi, I'm kinda new to options trading and wanted to get some experience before trading real, so I'm just using paper trade on SPY. I've met some problems that hope someone can enlighten me on

1) moomoo canceled my trade after expiry.... I'm guessing nobody is buying?
2) do u all usually buy longs or shorts for options? itm or atm or otm? delta 30 or lower?
3) is there a mentor that I can learn under?
4)kinda broke now so is there a minimum sum to start?

would appreciate any advice.