Hmm.. It's fairly last minute so I'm guessing you don't have a lot of time to work on it. I'm also not sure what you have at hand. In any case, here's what I'd think of doing.
1. Matching color shirt and pants. A color somewhere near gold would be best. Some shades of tan may be close enough to gold.
2. A football is a must, painted gold.
3. Old tennis shoes painted gold would be a nice touch.
4. Gold face paint on face and exposed skin. Just make sure it is safe for use on the face. Some body paint is not intended for use on the face.
5. Spray his hair with gold hair spray and/or spray an old football helmet gold.
6. Strike a pose!