I started HRT when I was 21 or so. I got top surgery a year or so ago (wild to me!) around 27 years old.

if you want to start, search "Erin's informed consent map," locate a place near you (or a local planned parenthood), confirm they take ur insurance, and then make an appointment. it's not difficult to start HRT via informed consent.

surgery is not that much more complicated mostly. look into local trans groups/state trans groups and see who they go to for top surgery, and then check to see if they take your insurance. schedule a consultation, and during the consultation let them know that you want to surgery, what you'd like, that you're not ready to set a date yet, and that you're trying to get more info about whether they can provide the results you'd like and what information they need from a therapist, letterwise so your insurance will cover it. you don't NEED a letter but it's a lot cheaper to get it if it's covered by insurance, and I think therapy in general is good for trans people.

that all being said, you can't get "HRT over with" as soon as possible - starting it will be frustrating and exciting and come with so many changes and not enough changes and looking in the mirror and trying to see if you look different and feeling like you don't and feeling like you're in your own skin for the first time in years. personally I recommend not thinking of it as something to get over with, though. you'll turn 19 and 20 and 21 when you turn those ages. you're just changing the direction you're going in.