Amyy - have you tried selling things you no longer need on EBay? You could get your Mum or Dad to set up an account for you.
Maybe a car boot sale (I think they're called "yard sales" or "garage sales" in the USA).
Is there anything you can make and sell? Friendship bracelets or similar?
Maybe you could ask family and/or friends if you could do chores for them for a small payment. Mowing the lawn, weeding the garden, car washing, cleaning windows, etc.
Hope that helps.