I always do sound and dialogue first. In fact, I'm one of those rare animators that tries to do 100% of their sound at the onset - I don't do a scratch (temporary) track. The only things I don't fill in are footsteps and variable body-on-environment sounds, like a sleeve dragging across a table.
Some people prefer just to have dialogue or their music to start with. Japanese anime tends to animate first and dub sound over the finished product. There's no "right" way to do this kind of stuff, but I personally think starting with sound is easiest.
Then you'll want to do what's called a leica reel. A leica reel is a story board timed out to your sound. It'll help you establish staging and action and see if your story is working. Do some backgrounds and set up whatever animation elements you need. Then it's time to animate!
thanks a lot, this is pretty much what I was thinking of doing. (possibly will do it but I will wait for more information, if any, comes my way)