What website is the best to buy scooters?

Electric or gas?

Craigslist, possibly Ebay.

You cannot buy new GOOD scooter online. All the decent manufacturers use dealer networks.

If you are seeking a street legal scooter . . gas:
http://www.bandit-motorsports.com/index....
http://scootersus.com/50ccscooters.html

Unless you are a mechanic, have no problem taking apart carbs or doing your own diagnostic checks, don't buy anything on line. Check out the local dealers and used market. Craigslist.org, ebay, your local paper, etc.