You shoudl definetly play the first one. You do not need to technically, but if you love good stories, than YOU HAVE TO!
Dragon Age was one of the best game that I ever played, I loved just spending hours not fighting but just talking with my party. It felt... real!
I wouldn't lose if I was you the opportunity to add this depth to the succession of the game, for sure the consequences of your choice in DA1 will have repercussion on DA2. It absolutely make sense to increase sells and to make the game more interesting.
DA2 it will be technically different, they made various modifications respect to the DA1, one of this is not able to create the character face (I just saw on the website that there is an addon feature that will permits to do that, but you will start as the standard DA2 character). But I am sure that many things like some combo spells or other features like giving gift to your party will be no different.
So my suggestion is try out DA1!