Reuben Walters would be a definite buddy for Sal, since he's big into gaming and has very strong opinions about movies and TV shows. I could see the two of them chatting up a storm about the merits of really schlocky B movies or the like. Reuben is straight himself, but he has no problem with hanging out with anybody. He's just a very chill guy.
Jeff Greene would be the sort to pick on Scott. He's a football player with a mean attitude who would get easily annoyed with Scott's sarcasm and put him up as a target of ridicule and scorn. He's not the sort to slam people into lockers, but he'd come up with derogatory nicknames and call him a loser if they passed in the halls.
If it's okay, I think it'd be neat if Sarah Burnhart was Oliver's girlfriend. She's also an adrenaline junkie and would be hooked on the racing scene in an instant, though thanks to her longsuffering dad, the car she owns is designed more for fuel efficiency than speed. Sarah finds card games to be boring normally, but if there's money on the table, adding a degree of risk, that's the sort of thing that piques her interest. At the same time, she's got her own interests in things like paintball and rock climbing that she'd want to expose Oliver to.