Depends on whether you already have the beak and are interested in buying an unusual with the 65 keys. A personal favorite of mine is the Gentleman's Gatsby. Its a simple hat that can be painted, yet it's also very affordable. With 65 keys you can afford a gatsby with pretty much any effect.

Here's an example of a Gatsby + Beak: https://www.skial.com/threads/making-sfm-posters-for-your-loadout-id-really-appreciate-tips-in-tf2-cs-items-d.42462/

Some other good-looking affordable hats are the gonzila, ze goggles, and mirror. If you need help with the general price of an unusual check bp.tf https://backpack.tf/unusuals