a dash dance is used to make the opponent think your going to attack them, baiting them into making a move and being counter attacked. I personally would suggest you focus on fundamentals more then the actualy character right now, practice consistently short hopping, wave dashing back and forth on platforms and shffling moves, read the article in here for Doc vs the world, possibly even make seperate files saved on ur computer for the matchups, but honestly youd benefit more from fixing your inconsistencies in techskill then focusing on reading, char matchups, etc.
here are some fake examples of reasons why we should focus on fixing our techskill
E.g. you want to short hop back air the opponent, you accidently full hop, you get juggled then forward smashed to death
E.g2, you want to wave land on a platform, you accidently roll and get punished
E.g3 you're dash dancing and **** up and end up doing the weird turnaround thing in front of ur opponent giving them a free grab into a wobble into death
Melee is based on mistakes, and character matchups, but foremost, mistakes
When i started getting heavy into doc, i referred to this video alot, it has and still helps me to this day to remember my options and possibilities, i suggest watching it, and taking in the info, than watching it again
http://www.youtube.com/watch?v=qp_qhEx3zKE if you have trouble with any of the techniques listed just ask here or refer back to the video