The right sign for "top" is going to depend on your sentence and the
meaning you want to convey.
I'll show you here the general sign for "top" but keep in mind that
this sign usually refers to "the highest point, area, or location."
TOP (at the top, highest point)
Notes:
If you mean "the best" then see: BEST
You can learn
American Sign Language (ASL) online at American Sign Language University ™
ASL resources by Lifeprint.com © Dr. William Vicars