I have been to dozens of dnb events so I think I'm quite well poised to answer this!
The whole ethos behind a dnb event is that it is all about the music. Therefore, there is no dresscode and you should wear what you feel comfortable with. Glowsticks might be taking it too far, unless it's a massive event, say in SE1 in london or something. Most lads wear jeans, maybe combats, a t-shirt, maybe a hoody, and most girls wear similar. It would be very rare to see a girl wearing a shirt or shoes, or a girl really dressed up (depending on the event/clientele of course). Although girls might wear a nice top etc. In general, just go casual. Wear what you feel comforatable with. And that means trainers really, or at least not heals, else you won't be able to dance.
As for the dancing, people just do whatever. Really. That's the beauty of it, no one hoenstly gives a ****. Make your own move up! People just generally bop to the music, and go nuts when a track comes on they particularly like. Copy your mates, or if you're not sure just nod your head.
Be prepared to get pushed past, depending on how busy it is. The toilets will likely be grimey. Towards the end of the night, if a lot of people ahve been taking drugs, you might see some messy people. Don't worry about that, they generally don't mean no harm.
Lastly, enjoy. The feeling of dnb in a club is awesome. It was meant to be played loud with lots of bass to shake your body. You might just get hooked.