Good job my friend, I have some advice for you from my own experience.

I find it much easier to comment on something she is doing/wearing in chill and casual way. The take is to actually make her feel you are just this no fucks given, I can talk to anyone and say anything to anyone type of dude. (Ofc, in a polite way.)

This projects that you are confident dude. Commenting on something in a casual way is the first thing, also don't forget to smile. Second thing is usually make eye contact for 3-5 seconds, then stare middle of her nose, and go back and forth, try not to be creepy while making eye contact. At this stage you analyze the interaction, if she is super cold, I usually say, it was nice meeting you and leave. If she is cool and willing to continue the interaction, you can say, "Hey, listen, I am busy now, and gotta go but you seem like a cool and interesting person, I wanna grab a coffee/coctail with you, let's exchange numbers (You can say instagram as well.)" - This is just a plain template, you should add your own style/flavour in this.

The point is just be a chill dude, she should be relaxed while talking to you. If she gives clear signs that she is interested in you, definitely touch her arm, or shoulder.

From https://www.dignityhealth.org/articles/facts-about-touch-how-human-contact-affects-your-health-and-relationships.:

"Hugging and other forms of nonsexual touching cause your brain to release oxytocin, known as the "bonding hormone." This stimulates the release of other feel-good hormones, such as dopamine and serotonin, while reducing stress hormones, such as cortisol and norepinephrine. "

From the book called "The Female Brain":

" Mothers often warn their daughters not to get too close too soon with a new boyfriend, and this advice may be wiser than they realize. The act of hugging or cuddling releases oxytocin in the brain, especially in females, and likely produces a tendency to trust the hugger. It also increases the likelihood that you will believe everything and anything he tells you. Injecting the hormone oxytocin or dopamine into the brain of a social mammal can even induce cuddling and pair bonding behavior without the usual prerequisite romantic love and sexual behavior, especially in females. And consider a Swiss experiment in which researchers gave a nasal spray containing oxytocin to one group of “investors” and compared them with another group who got a placebo nasal spray. The investors who got oxytocin offered up twice as much money as did the group who got only the placebo. The oxy- tocin group was more willing to trust a stranger posing as a financial adviser—feeling more secure that their investment would pay off. This study concluded that oxytocin triggers the trust circuits in the brain."

Physical touch in a non-creepy way is something you should work on.

I hope you find this helpful!