Think how lucky you are for finding out now what a piece of trash she is, rather than 10 years down the track. I'm 32 and very happily married, so without boasting too much I've got a bit more experience in these matters than a lot of the teenagers that post on web forums (in some matters - I wouldn't, for example, expect to give better advice than them on how to pick up someone that age, as I'd be culturally out of touch). I'm also from a country where we're pretty liberal about sex, and so I've had several multi-year relationships prior to my marriage, and a fair few short-term flings as well.
I know that right now you'll struggle to see things this way, but it's the truth: you got very very lucky. There's millions of guys out there whose WIVES left them under similar circumstances. Not g/f's, but WIVES, and that means them taking half the house and all the kids, after taking off with some guy they met while you thought that they were having quiet drinks at one of their g/f's houses, or while they were on a business trip. You found out the best possible way: when there is nothing long term that can really get fucked over by it.
It always sucks to find out that the person you care about is shallow, but it happens, and the sooner you realise that's what happened, the sooner you can realise that you got it lucky and that you can do better than that. If you're all revved up for revenge, don't do anything stupid like prank call her phone, or stalk her or anything shite like that - she'll be her own punishment. The world is full of women who used to be hot when they were younger, but were shallow as hell, cheated on guys better than they deserved, and are now 38 and single and suddenly wrist-slittingly miserable because no guy even looks at them anymore, and they don't exactly have the personality to make up for it. Whereas nice, sweet people never struggle for relationships as an adult (unless they are truly obese, in which case they can work on that via exercise or lapband surgery if desperate - and even the fattest folk I know have had awesome marriages so long as they're looking to marry someone who's sweet rather than a cliched model look) - both guys and girls tend to fall over themselves trying to get the 'nice/sweet' folk once they hit a certain age and start thinking long-term.
If she's the kind of b**** that breaks up by text over the phone and immediately hooks up with someone else (and hate to break it to you, but she was probably already cheating on you with him), then you can place money that at around 35 she'll be crying 'why aren't there any decent men out there' (it's because you burnt them when they were young enough not to recognise you for what you are, b****, and now they know better than to go near someone like you!).
I don't know how old you are, but if you're anywhere in the teenage years, maybe up to 20ish even, you're going to have feelings for her anyway, but they'll go soon enough, so long as you keep reminding yourself that she aint worth having feelings for.
Go out with friends is good advice - take it. DON'T try to rush into a new relationship. Rebound flings are great when you're older (like late 20s onwards) when both parties know exactly what it is, you both know it isn't going to last past a bit of sex until both of you feel better about the person that dumped each of you last, and you can then move on without having hurt anyone's feelings. Rebound relationships before then just mean that you're going to hurt whoever you're with in the same way that you got hurt. Get used to being single again first. Then, once you've stopped having the urge to constantly look for a new partner, THEN start thinking about dating again.
The biggest 'warning, b**** ahead!' sign is the fact that she TOLD you that she is looking to go out on a date with some guy she met in a club, and how crazy she is over him. Sorry, but if you've only met in a club, that means she's hardly talked to the guy - he might be hot, but unless she's the most shallow person on earth, she couldn't possibly be 'crazy' over him. She's specifically saying that to make you feel jealous so that she can get more attention from you, so she can then get the powertrip of turning you down even more. Don't fall for it. Just take it as further evidence that she isn't worth it, and that you got lucky when you got out of that relationship. If I had just broken up with an ex, even a short-term relationship, and I was about to go out with someone else, I'd keep extremely quiet about it until I knew for sure the relationship was going to last, and I certainly wouldn't rave to the person I dumped about how great the new one was. That's because I'm not utterly shallow and selfish, and hence I would care about my ex's feelings and wouldn't want to hurt her by making her feel inadequate compared to the new g/f. ANY decent person would think that way. Your ex is quite clearly NOT a decent person.
You've done very very well to be free of her. You're now free to use your experience to find someone who is actually worth spending your time with. But take the time to enjoy being single for a bit first. Then use your experience to avoid the same mistake happening again. Don't expect to find a serious g/f in clubs or somewhere where you can barely talk - meet them through uni/college, common hobbies, friends, work and so on. You've dodged a bullet by leaving that relationship. It doesn't feel like it right now, I know. But in a few years time, you'll look back and think about how lucky you were not to still be stuck with that girl.