Having raced both karts and Skip Barber (at around the same age as you), my opinion would be to start in karts. Like you said, you’ll get more seat time in a kart for less money. This will let you develop skills like race craft and consistency so you’ll be able to focus on learning to drive the car when you make the move to Skip Barber. In addition, making a big mistake in a Skippy car can easily double the cost of a race weekend (which isn’t cheap to begin with). It’s much cheaper to put a new axle in a kart than a new rear end on a Skippy car.
On top of all that, when I used to race Skip Barber they did an annual “karting shootout”, which I’m assuming they still do. Anyone under a certain age who raced a kart in the past year could show up and participate for about the cost of a normal Skip Barber race weekend. The top three finishers received credit towards future races, and the winner was awarded a fully paid season in the Skip Barber national series. Not too shabby.
Hope this helps. Best of luck!
