Oooh, from the beginning! Great!
What fish you can keep will depend on the tank size, so figuring that out should be first priority.
Live Sand... Ok, I admit that I used live sand in my first setup, but I probably wouldn't bother in any future ones. Essentially, if you put in plain old aragonite sand and a single piece of live rock, within days, all your sand is "live sand" so I don't know that paying the extra money is worth it. Also, you have to consider how much of the bacteria and other critters are really still alive after the sand has been stored in a bag in a warehouse, shipped in an unheated cargo plane, stored in another warehouse, then sitting on a fish store shelf for a week.
Now, it certainly doesn't hurt anything, and it might liven up the sand bed faster than plain sand, but you can save money by buying mostly plain aragonite sand and maybe layering a little live sand on top.
Anyway, back to step one. Figure out what size tank, and where you'll be putting it. Will this be Fish Only (FO), Fish Only With Live Rock (FOWLR) or a Reef setup? Reefs are the prettiest IMO, but some fish are not reef safe.
Once you have tank size and type decided, then it's time to figure out what kinds of fish and start the cycling!