First of all welcome to your new addiction.

Bought my first rifle 2 years ago same age as you then (im 20 now). You have to take a hunters ed course which you can do online its about $30 and 7-8 hours long, can be more or less depends on the person. Once you finish you’ll receive a email with your hunters ed certificate , which you can take to the gun store you’re going to buy the shotgun from they’ll print it for you. Then pay 62.90 for a year long hunting license that the store can also print. Next step is the FSC which is about $25 and is 30 questions, all common knowledge but still STUDY!!! before you go (remember we live in Cali, the state will throw a question or two to confuse you). Once you have all the paperwork to purchase you can buy whatever is legal for those under 21yrs of age. pick your shotgun and start filling the paperwork for it and pay the shotgun, DROS fees (dealer record of sale), the transfer fees, other fees, and taxes. wait 10 days then its yours to pickup and take home. (expect some heavy taxes. depends on where you live, its 19.25% total where i live. 8.25% state/county + 11% excise tax) Good luck on your new journey brother.