At 16 years of age you qualify to race with the big guys
I would strongly suggest to start with Yamaha KT100 at the Senior class , or a TAG class with Rotax, Leopard, etc 125cc class.
I urge you to give the local track a phone call, or send them an email to see what’s available to you.
All of us here at the forum are from many different states ( Nation Wide )
But also have racers from all over the world. So every state, every town in the same state may have totally different classes from anything I could recommend to you. That’s why it is so important to contact them and see what they run there, and how big the class is.
I downsized on my shifter karts ( we had 4 of them ) because there was no class in my town ( local track ) and I also liked the club here where they ran spec Yamaha KT100, not to mention I’m getting older, and shifter karts are brutal to drive at sprint tracks, even with my years of experience.
It all depends what club you wanna race in.
NorCal kart club has a nice mixture of venues that include shifter karts 125cc and 80cc, along with the TAG karts. And the do a lot of big track races (Road Racing), which involves racing at big tracks where Indy Cars, and race cars run.
But once again, You need to contact them, as there are way too many classes for us to give you a good advise.
If I were you, I would go to that arrive and drive program that you already are scheduled to do anyway, and while you’re there, I would totally talk to people and ask them about the club, the types of karts and engine packages you should run, and the ones that are more fun and enjoyable to do that will suit you.
And once you do your first arrive and drive event, a lot of your thinking is gonna be different from our recommendations here at the forum, and will also open your eyes and may decide that you like a different engine package or a different class.
I can tell you form a personal experience, I’ve ben driving tons of different karts, engine packages, many different chassis manufactures, and when I made the change from shifter karts to KT100’s, I thought I was gonna dominate the competition! Well let me tell you I GOT MY BUTT KICKED LEFT AND RIGHT. As it was a steep learning curve for me, but I got better at it with more seat time, and tuning my kart differently, and changing my driving style. I will honestly say that a KT100 will really teach you how to drive.