I wouldn't recommend ace bandages. They have a history of leaving bruises and even broken ribs in their wake. Duck tape is also a bad idea since it doesn't have any give. You can always go the route of buying a binder made specifically for your chest from a store like Underworks, but if you're like me and don't have an extra 35 bucks to spend, I'd check out the binding threads in the crossplay forum. There's two main ones, and several smaller threads floating around. They should be able tell you all you need to know about binding, as well as a safe method for using ace bandages if they're your only option. Good luck with your crossplay!
Sherlock Holmes: How dare you be rude to this woman who has invited us into her tent, offered us her hedgehog?
Dr. John Watson: Says the man that throws women from trains.