Welcome to AA!
For live rock, if you want to save a few $$, order some dry "live" rock from Marco rocks
. This is real nice rock that was once live and is now dried out. It will cycle your tank like uncured live rock would. I would suggest getting about 100 lbs of Marco rock then just buying a few lbs of live rock from your lfs
to seed your tank.
As Speed mentioned, you can just buy dry aragonite sand, or even playsand if you want and then get a cup or 2 of live sand from your lfs
or from a local reefer if you know any with an established tank. It's not really necessary tho. The dry sand alone would work fine.
Skimmers come in a wide variety of prices and performance. Depending on your budget, I would suggest an Octopus NW 200
if you want to spend around $200. There really isn't a skimmer made that costs less than that, that will perform decently. If you are able to spend more, how much more, and I can recommend a higher end skimmer.
Depending on what you want to keep, I would suggest at least 2 Koralia 4's for powerheads.
What are your plans for lighting? Try to look ahead. Many people end up buy multiple sets of lighting because they find the "cheaper" lighting they started with isn't good enough for some of the corals we all like to keep. It's better to spend more up front to buy better lighting now instead of having to buy upgraded lighting down the road.