When I was a kid, we had all sorts of dogs because my father was a vet.
My two pennies.
1) Jack Russells can be a lot of fun, but some have a nasty streak. I never forgave the one that went for my boiled sweet, aged five, and ripped up the end of my finger.
2) Border Terriers are lots of fun, but go for a dog not a bitch. The females have issues. Our best dog ever was a boy.
3) Rescue dogs can be quite wonderful. The problem is that if the previous owner was a complete sadistic bastard, the dog may be really badly scarred emotionally, and may never really recover. Some do, and are quite wonderful companions for the rest of their lives.
4) I'll probably be arrested, but males are a whole lot better than females when it comes to canine temperament (Tin Hat)
We have a Lucas Terrier. A complete anarchist, and he doesn't really give a stuff about anybody, but he is small, friendly, and great fun to be around...unless he sees a cat or a squirrel.
One last thing, if you get a male, do not ask the vet to cut his balls off. I wouldn't like that, so why inflict it on your new pet?
Good luck