Drive on. It could be the gas cap but if it isn't running any differently then no worries unless you have to pass an emission test. A new gas cap could be a good idea anyway. A 1999 is 15 years old. The rubber ring in the cap that seals to the tank filler pipe is probably hard, cracked and...
I would get a car first. Yeah it will use more fuel and not be so much fun but it is good to be a car driver first so you know how bikes are harder to see and how they move through traffic, then when you're on your bike you have the car drivers perspective in mind and you can drive more...