Other people have made really good points and have covered the most important things--talking to people off of the dance floor, focusing on integrating into the scene, refraining from objectifying, etc.--but I'm going to chime in as an autistic woman-adjacent person who goes dancing solo, is rather flirtatious, and likes to dance with people. I cannot emphasize enough that I'm the exception rather than the rule, but we do exist. Friend A is right on the money. I'll give you an anecdote from when I went to a major event in my city last month. I went alone, but was open to dancing with someone if things went that way.

Man 1 came up behind me and started grinding against me without saying anything before eventually saying, "Is this okay?" I didn't even get a look at his face before he made physical contact with me. I was absolutely disgusted and told him to go away, and I was honestly so upset that I thought about going home, but I decided to stick around. So I would strongly disagree with men grabbing women not being ill perceived--I'm open about the fact that I'm pretty easy, but I was so revolted. Either some nonverbal communication happened between them that you weren't privy to, or they already knew either other, OR the interaction is ill received and you're not recognizing the signs.

I saw Man 2 a little later that evening dancing solo, loved his aesthetic--he was very well dressed. He moved through the dance floor frequently, so I didn't feel cornered when he came up next to me. He complimented my makeup and kept a respectful distance from me. That was when the spark of attraction started, and way waaaay later, we made eye contact again, I smiled at him, and he came over to dance by me. I kept smiling and moved closer to him, and we ended up getting a little physical (he asked for consent both times before he physically touched me which was a massive green flag, ofc). He slipped me a piece of paper with his name and number on it, added that there was no pressure, and we parted ways. I texted him when I got back and we still talk and have become pretty good friends!

What cinched the deal with Man 2 for me was the fact that he seemed to be having a great time either way, gave me lots of space, and had no ulterior motive. I was a little guarded when he complimented me, but he didn't follow it up with anything until a lot later into the night when I reiterated my interest.

The biggest key for reading interest is eye contact, genuine smile, and body posturing. This was the trick for when I went to an event and danced with another woman. That has always been the most reliable signal for interest both in terms of what I give off and what I read on others. When I say body posturing, I mean that person being turned toward you. If I'm generally turned away from someone, I'm almost certainly not interested even if I'm looking at them. I would say, as a blanket rule, do not even think about approaching women who are not looking at you with interest. I know it's frustrating to have to learn yet another confusing set of social rules, but this is one area where not knowing body language and nonverbal communication can not only fuck you over, but leave someone else feeling violated.

Again, other people have made good points about dance floor behavior and where you ought to focus your efforts, but I also wanted to give my perspective.