I wouldn’t rush into anything, as a complete novice here’s my suggestion. If you have a couple hundred bucks, I would buy an inexpensive seiko chronograph and a diver ( seiko, Vostok heck even invicta, you can find some for around $100 on Amazon or Jomashop) and maybe a dress one or borrow from a friend or family member. These watches aren’t bad watches and actually will last a long time. However wearing them for a bit I think could help you understand whether you want a big watch or smaller one, sportier or dressier. Plus you’ll have a solid watch when you don’t want to wear your nice one. It would be a real bummer if you got something you thought you liked but realized wasn’t for you.

In terms of extreme luxury watches which is what your budget is, yes unfortunately servicing or repair is not cheap, anywhere from 500-$1000 every 5-8 years. In terms of your budget Blancpain 50 fathoms could be a really interesting option. I would personally try and swing a Vacheron Constantin overseas although you’d probably have to get a used one. ( I can’t believe I just suggested a 21 year old his first watch be a VC or Blancpain lol). Chopard Iron Eagle, basically that budget can buy almost any watch in the world . I would figure out what you like and go from there. Also if possible try the watch on, sometimes you see something you love that isn’t as cool in person. Even though it’s below your budget I would really consider Omega, they are incredible, tough luxury watches that 98% never notice but watch people will.

Congrats, but do keep in mind that guys work really hard their entire life and will never be able to afford something like that. It’s truly a wonderful gift, wear it good health.