I know that it seems expensive at first, so either buy "bigger" than you'll think you need, or get components that are easily upgraded.
I mean, don't get two kegs and one WYE fitting, if you think that you will only have two kegs on tap. Oh, the one WYE fitting is fine, but always have one keg more than you plan on having on tap since you will need to clean one and then carb it up.
Some things you don't need- a second regulator unless you really want to serve a wit beer at 16 psi and a stout at 9 psi. I serve 6 taps at 12 psi. It's cheaper, with one regulator and a distributor. Or, if you're serving two, just the WYE fitting.
You absolutely need to have check valves. Do NOT buy a set up without them.
I agree that you need perlicks right from the start. I know other faucets are cheaper- but they stick. If you're not pouring beers often (several times a day in each faucet), they will stick closed. Perlicks are forward sealing and never stick- that's one splurge that is always worth it.
Go with 12' lines, no matter what anybody else tells you. 12' of 3/16" beerline for each tap. Trust me- you met me on the internet so right there that proves I'm trustworthy!
Seriously, just look at the "foam" posts in this forum, and you can see that almost all of them are from folks who bought their setups preassembled with 5-6' of beerline. Don't do that- when you order, ask for 12' of line for each tap. I bought my setup from kegconnection.com, and ask them to do that since my setup was preassembled. They told me I didn't need that- but I insisted. It was a lot better than the other setup I got with 5' of line! Then I went to 6', then 8' and finally 10' on that set up. Um, yeah- it would have been MUCH cheaper and less of a headache to start with 12' and have it done. So go with what your gut says is right in the first place. Beerline is cheap, but it's a pain to change later on when you have multiple taps. Just do it right the first time.
If you're going with an upright fridge, those are easy to convert as there are no lines in the door. Freezers are awesome, but require a temperature controller and possibly a collar. The reason for an upright fridge for me wasn't that, though. I love the look of a keezer, and the fit in the house would be better. For me, I'm 50 years old and have trouble lifting full kegs and carboys in and out of a chest freezer. An upright is much easier physically for me, although far less attractive. My kegerator has a definite "college party with taps out of the fridge" look to it, while keezers can be attractive even in a living room. So think about that if you're married, or if it's not going in the garage.