I would just like to know if I buy a gasoline trike then is it compulsory to have a license to ride this?

Depends on what kind of "trike" you want to buy. If it's a three-wheeled ATV, then NO. You can't ride it on public roadways. If it's a three-wheeled motorcycle, then you'll need a motorcycle operator's license to ride it, and it must be licensed and insured as a motorcycle. If it's something else, then you'll have to ask your local department of motor vehicles.