I'm kind of in the same boat you are, just putting together my first keezer, and trying to learn and absorb as much as I can. Here's a few snippets I've learned / believe that can maybe help you out:
First off: before you even begin, PLAN! Decide how many kegs and faucets will ultimately fit in your chest freezer, whether you're going to put your gas bottle and regulators inside or outside the keezer, whether you're going to go with only CO2 or with a CO2 system and a nitro system, etc. Make a plan, buy your stuff to fulfill that plan, and ONLY buy stuff that will further that plan! But make that plan flexible, in case you really couldn't fit that many kegs in it, or in case you have to mount your shanks in a different location to accommodate the ability to pull your kegs in and out, etc. What model chest freezer BTW? There's a post somewhere on here that shows diagrams of many popular models and what all can fit in them.
Faucets: people who buy crappy chrome plated faucets always find that they start to flake off and eventually upgrade. Just start with stainless steel (preferably forward seal) faucets and they'll last through all your future keezer / kegerator updates.
Another note on faucets: If you were to get flow control faucets, your lines may not need to be so long. I went with Perlick 650ss and 5' lines.
Shanks: same deal, start with stainless. People say to get as long as you can in order to create a nice cold mass of steel for that first pour to sit in; but length is going to depend on how your collar is built, etc.; and on a keezer especially, you got to make sure you don't go so long that you can't get your kegs in and out! That is, unless you build a whole new lid that actually contains the shanks and faucets as it tilts up, but that's not a beginner topic.
Another item on shanks: they do make shanks with integrated nipples (instead of that use a tailpiece); but I personally decided against them for at least three reasons: 1) If I bust off a nipple through some sloppy keg-moving, I'd have to buy a whole new shank. 2) Can you run a cleaning brush through a shank with an integrated nipple? 3) Tailpiece type can be changed from barb to flare if you wish.
Regulator: I'd say just start with a single primary with a "wye" (or a 2-way manifold) that leads to two check valved shut-offs. Start off your 2-keg adventure with similar styles that can be carbed the same. As I think has been said, in a future update one leg of the wye (or 2-way manifold) can be dedicated to keg purging / force carbing duties, while the other leg feeds a multi-way manifold or multi-bank secondary. I went with a Taprite primary with wye, my next update will be a multi-bank of Taprite secondaries (and more kegs of course!)
I guess if you absolutely NEED 2 different pressures right off the bat, a dual primary is not a bad investment. As was also said, upon later upgrade that second primary can be used to reduce the number of secondaries you'll need.
And yes, I believe check valves between any keg and any regulator are very important so as to not run beer up your gas lines and screw up your regulator.
Barb versus flare: I want to be flare everywhere possible, for two reasons I can think of: 1) you can build all your lines "at the bench" instead of shoving tubing on a barb while hovering over your keezer, breaking **** when your hand slips. 2) You can have spare lines pre-built that can quickly and easily be put into service with just a few turns of a wrench. Me personally, I didn't realize I wanted all-flare when I started acquiring stuff, so right now I've got kind of a mix of flare and barb. Standardizing everything to all-flare is my next, next upgrade--if I had it all to do over, I would have gone all-flare from the outset.
Lines: seems like the standard is soft-tubing gas lines that are 5/16" ID / 9/16" OD, and soft-tubing bev lines that are 3/8" ID / 5/8" OD. In that size and style your choice seems to be basic vinyl (PVC) or PVC-free barrier-style tubing. I went with the PVC-free, because it'd suck if my beer tasted like vinyl.
Another note on lines: many people have gone to polyethylene hard-tubing and John Guest fittings for the bev lines, and even for the gas lines. I can see the benefit of quick and easy line changes (especially on the bev side), it will transfer no plastic-y flavors, and the line itself is generally cheaper than any but the suckiest vinyl lines. I guess there's also the benefit of being able to color-code everything to avoid mixing up lines and such. And also if you're running your gas bottle outside the keezer then the holes you drill for the lines can be smaller. For me: if I'd realized poly tubing was an option at the outset, I might have designed for it--not such a huge deal for me as my gas is inside the keezer, and I plan for it to always stay inside. As it stands, I see it as maybe a future upgrade kind of thing, after I've exhausted all other keezer
spending upgrade opportunities
A few others: Seems like no one place, no matter how well-stocked, sells
everything you want to build your system just the way you want it. Also, you'll find that Place 1 has Item A for $25 and item B for $5, while Place 2 has identical Item A for $5 and identical Item B for $25. And Place 3 has both items for $1 each, but wants $30 for shipping. And if you call a manufacturer with a technical question about a part or assembly 3 different times, you'll get 3 completely different and conflicting answers. And if you're lucky, when you buy the thing you'll find out that one of the 3 answers was actually partially correct!
I hope that was helpful.
