My personal opinion is that magic (or anything else, really) should never be a substitute for a personality.
It really isn't hard to learn to talk to people. And here's the crazy part - if one takes the time to learn those social skills, their magic gets significantly better.
People who use magic to start, maintain, and end conversations are seen as one-dimensional. Magic is all they are to others - so if someone doesn't want to see a magic trick or talk about magic, they don't want to talk to that person. I've had a few friends like this, where I have to decide before I contact them if I'm ready for an hour long monologue on the inner workings of the newest gimmick they're making or routine they're practicing for their show. It's not that I don't care, it's that I have interests other than magic, too.
So my response to "What trick should I use to start conversations/ask this girl out/propose/etc?" is "Don't. Just talk to them like a normal person so they realize you're not a caricature."