There are a lot of 125cc-150cc scoots that don't weigh much more than a 50cc. I occasionally see Agility 125's being sold with low kms/miles for under $1,000. It would probably be cheaper to sell your 50 and buy a used 125 than to mod the 50, and you'll end up with a faster AND more reliable scoot.
If you're trying to avoid having to get a motorcycle endorsement, then you shouldn't be going faster anyway. Learn the material, get your permit, and take the MSF Basic Rider's course. It'll make you a better and safer rider, thus making it more likely you'll be around to enjoy your faster scooter for years to come.
Otherwise, the best way to go fast on a 50 is a 2 stroke model that has been derestricted, has a set of Dr. Pulley weights, and a tuned pipe. Again -- this will all cost you more in the long run than a 125 or 150 stock.
Just my humble opinion.
Good luck, and RIDE SAFE!
Jay