Set up a donation drive with your school or organization. Establish start and ending dates for the drive. Declare in all communications that, in lieu of money, used cheerleading uniforms -- in decent shape -- are desired. Hand out fliers and advertise in the local newspaper or on the radio to spread the word. Reach out to other local schools or cheerleading groups and ask about acquiring their old uniforms.
Establish a cheerleader uniform agreement with all current participants. Offer a reduced fee for purchase of any uniform on the condition that the buyer will donate the outfit back to the program in mint condition at the end of the year. Add a space at the bottom of the agreement for a parent or guardian to sign the agreement if the participant is under 18 years old.
Ask family or friends who have cheered in the past to give up their old uniform. Tailor the uniform yourself or offer to pay for alterations in exchange for the donation.