UK Stamps... USA Stamps... Can anyone help me?

[Hysong123]

How many stamps do you need to put on an envelope to UK if you are from the USA? Because I want to send a regular sized letter with 2 dollars to Ryan Turner, Bertie Gilbert and Bonnie Wright requesting for an Autograph. Do you think they'd still send me an autograph even if I just send a LOR with 2 dollars? Is there an easier and cheaper way to get their autographs because I understand they do a lot for us and we SHOULD pay for the stamps but you know... any easier way or cheaper way 'cuz I'm running really low on stamps. if there's no way i can do an easier way, then I'll just have to do the 2 dollars method. Please help!