I've spent well over $7,000 for my 90g and while I've gotten decent equipment nothing has been top of the line. For a 100g tank I'd plan to spend $5-6k on equipment alone, before you start adding in the cost of livestock, electricity, and water. In comparison, I've probably spent close to $800 on my 10g tank (including livestock). Bottom line, saltwater isn't cheap.
I'd add a few things to the list Northstar started:
Skimmer
RO/DI unit
Testing Supplies (liquid kits, not test strips)
GFCI outlets or adapters
Powerstrips
Mag-float or scraping supplies
airline tubing to start a siphon when you clean the tank
pcv pipe, valves, and cement/softner for setting up the plumbing for your sump
return pump for your sump
overflow box if your tank isn't drilled
step ladder to stand on to reach the bottom of your tank (or a sturdy chair)
a light for your sump (this can be a clip on shop light)
And for a 100g tank, I don't think I'd go without a sump or skimmer long-term - a few months is okay while you get it set up, but I wouldn't go much longer than that.
Another consideration for a tank that size is whether the floor you plan to put it on can support it - 100g is a large tank and you might need to reinforce the floor - you're talking 1800 or more lbs of weight in a 4'x2' area of floor. I put my tank at my office, which rests on a cement slab, rather than in my apartment which is on the second floor of an older home, because I didn't think the floor at home could hold the weight. If you need to reinforce the floor, then you need to add that cost in as well.
Once you add livestock, then you need to start adding the cost of fish, cuc, corals, chaeto, food. For my 90g tank I am now finishing my 3rd bucket of salt, and my tank has been up and running for 6-7mo - each bucket is $50. Again, stuff adds up quickly...
Have you read this article yet?
https://www.livingreefs.com/basic-equipment-list-t19611.html
The only things on here that I don't think you need immediately (and can do w/o long-term if finances are a concern) are the auto top-off and phosphate reactor.
How much money are you looking to spend or do you have to spend on the tank? Knowing that might help us point you in the right direction as far as equipment, etc. - there are certain things that you just don't want to buy cheap brands because they turn out to be more expensive in the long-run when they break or you have to replace them because they don't work (skimmers, powerheads, heaters, lights are good examples). Also, do you want to keep corals, or just fish - the cost of lighting will change greatly depending on which route you go. Like North says, you really need to have a well-developed plan before you start.
Welcome and good luck!