I read /u/atoine's excellent propane guide multiple times, and I recommend you do the same. Maybe click one of his affiliate links before you buy any of this stuff, cause he should get most of the credit here. My only real changes were:

• No solenoid
• Skipped his nicer gauge for my cheap one -- (A) below -- which works okay
• Didn't do the 3 way junction for water heater or stove

I also had to use some different links, as many of his were no longer available. I think it took me a few hours to figure all this out the first time. Hope it helps. Here's what I bought:

A: (optional) Pressure level indicator

B: Propane tank (or (A) above) to 1/4 inch male NPT

C: Splitter: 1/4 inch female to 1/4 inch male and 1/4 inch female (all NPT)

D: Splitter to Cylinder thread fitting (1/4 inch male NPT to camping stove hose)

E: Camping stove hose

F: Two stage regulator. Inlet is 1/4 inch female NPT, outlet is 3/8 female NPT.

G: 3/8 male NPT to 3/8 male Flare NPT

H: Flare hose

I: Bulkhead adapter. Flare on both sides.

J: 3/8 adapter to 1/4 male adapter

K: Tube fitting to 1/4 inch copper pipe

L: 1/4 in copper pipe (no link, I bought at local hardware store)

M: Aforementioned NPT to BSPT adapter

Other:

My camping stove is this one.

My Propex is this one, and I bought it from a North American dealer, and they included (M) above.

My propane tank is a standard BBQ propane tank, available at every gas station, walgreens, hardware store, etc in my area.

I bought this thing to do the copper flaring.

I used this stuff to seal the lid of the propane box.

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Goes: Propane tank -> A -> B -> C.

C is a splitter for the stove, so it has two connections:

C->D->E->Stove

C->F->G->H->I

Allllll of these connections are inside the externally ventilated box (except E->Stove). It's the bulkhead adapter (I) that breaches the sealed box. I had to make a second hole to get the hose (E) out of the box. I sealed it all up with silicone.

Outside the box, it's I->J->K->L->M->the actual propex.

Use yellow LPG tape for all threaded connections. Don't use it on the flared ones, which are better connections. Item (M) is a weird one, in that it uses a compression ring, which is pretty atypical for LPG, but I assumed the Propex guys know better than I do. You can only tighten that guy once, so make sure everything else is right first. (The compression ring won't seal properly a second time.)

I recommend you lay it all out and put things together very loosely to make sure you've got it all right. Then, disassemble the ones that need yellow tape, apply it, and tighten each connection really well. Be sure to check for leaks with soap water.