How can you get your mom to let you crossdress?

Depends on the mom. Some are ok with it, others are not - often it depends on the Dad and the strictness of their religious background. Study your Mom and Dad - if they are open to you experimenting. Cross dressers are generally straight but they might think otherwise and have a problem with that so if you are straight tell them in case that worries them, and if not - think about it carefully. Maybe you need to think about it a bit more before coming out as gay to your parents. It's 2 different issues after all.

You can just try to start with little things and if they are dead set against it maybe you can get them to allow it at home. You can also get tips from other kids at teenlineonline.org. You can be anon there but there are all teens answering and there's also a forum.