Let it be a lesson to you. You can’t build chemistry. It’s either there or it’s not there. Infatuation is something you have to get over your proclivity towards if you want to have a mature relationship. If you’re attracted to a girl, talk to her. Get to know her. Figure out her situation. Ask about the things she wants out of life.
While you’re doing all this, what you’re looking for is a spark. If you know what you’re looking for, there’s no mistaking it. Your heartbeat quickens and your brain starts to shut down some. That’s when you know you have something. Look for signs of the spark in her too. If you feel it, touch her gently on the arm when you’re talking. See how she reacts. If it’s different then how she normally acts, then you might have something.
If you don’t feel that spark, or if she doesn’t feel it, then there is no chemistry between you and you can either just be her friend or you can move on. But there’s no point in dating her.
If you do, and you think she does too, that’s when you can try asking her out.
If you want to get your mind off of her, try talking to a few more girls. You’ll find a spark with one of them, and then you won’t be able to get your mind off of her. Don’t wait too long to ask her out like you did this one.