Wow. Your questions sound like mine from a month ago.
If I were you, I'd do MUCH reading before doing anything.
Go to
www.liveaquaria.com and look through the fish they have. They have good write-ups on every fish they sell, and a compatibility chart that tells what they will get along with.
For filtration, there's many ways of doing it. A buddy of mine has a tank he's kept running, trouble free, for YEARS now with an undergravel filter. It's the old school way, but also the cheapest, and if you are very careful, it's very effective.
The newer way is to have lots of live rock. With the live rock you also need good flow, to push the water thru the live rock, which is so porous that it has stuff growing inside and out, so when the water flows thru it, it filters it.
Skimmers just take out nitrates from the water. They make bubbles, and the crap that you can't see in the water is attracted to the bubbles and yadda yadda...
As for where to get equipment, your best bet (if on a budget) is NOT your LFS. Your best bet is in the classified sections of boards like this, or reef central or if you're lucky you might even have a local club with a forum.
You just need to read read read before you do anything else.