The first things I'd get him are a few performance driving courses at racing schools applicable to your climate.
As for the car, it's got to be something at least a little special. I have a couple of reasons for that. The most important is desirability; purely because his friends will want to ride in his car.
That will keep his friend count low, but more importantly keep him out of their cars, which will invariably provide an environment in which he has less control over the evening and is less safe. You can prepare him to handle fuckups (not prevent them, but handle them), but you can't prepare his friends.
In order for that to work, it needs a back seat. It's best if it fits four people comfortably, and five people incredibly uncomfortably. That will wind things down to "double dating" and a just few buddies hitting events, and encourage them to stay that way.
Something nice will also increase his credibility among various groups if he can't do it all on his own. Not too fancy, just a bit better looking than average; a badge the kids respect these days. I'm not sure what that is anymore, but I know most kids aren't as picky at this point.
Behind the rear seat is a big decision. Do you want him fucking in a sleazy hotel or a neighbor's house? Is the potential risk of being caught by a girl's father worth avoiding the risk of being caught by a cop?
Either way he's double-fucked, but in at least one event, the guy might just send him on his way.
Personally, I... No. You don't want to know what the hell I was like. You'd never let him leave the house.:rofl:
The sound system is an incredibly important part of the decision that you should be involved in. This is more important than it's ever been, and the car plays a small part in it.
You want that receiver to have Blutooth and voice activated everything.
Drop the cash, man. He'll just think it's cool, but you'll know his navigation, Internet radio, phone calls, and texts are taking place in the air and on the dash instead of in his hand. He won't have an after-market GPS impeding his visibility or becoming a projectile, either.
As for the rest of the system, let it be his business.
In order for Blutooth to work properly, you'll need a car that's decently quiet; and that means avoiding all the suggestions of old Land Rovers or out of date pickups. This is a new world, with new threats. Everyone needs a smart phone these days to remain relevant without too much effort, and the easiest way to keep it out of their hand is a fancy receiver.
I'd consider safety, as well. A Jeep is not safe. A Volvo is safe, but not necessarily cool unless it's a slightly newer model. The difference can be split somewhere by adjusting model years and vehicle types. The safer, slightly modern vehicles will land lower insurance premiums, which will take the shock out of a higher sticker price.
A great way to have a bit of control over his life without him noticing is very calculated manipulation during the first vehicle purchase. It might cost you a bit more, but you'll know you are probably avoiding a few talks and arguments simply by making certain actions easier decisions, and he'll feel more free.
With the performance training under his belt, he'll be more likely to survive stupidity.
Cheers,
Kennith