I posted a reply to a guy on the Chords Of Orion Youtube channel, and I thought it might be interesting here. So if you are a new ambient player, and have $400 to spend on pedals and stuff: Interesting challenge: as a 40 year guitar player, but who has only been into ambient guitar for 8 months, I'll give my two cents. So, assuming you have a guitar and amp and mic to record the amp (or you go direct to your computer), etc, in other words, we're talking about just the pedal board: then here's my suggestion for what you need:
1) A volume pedal: go with Chords of Orion favorite Morley Little Alligator: $60 on eBay
2) Delay: TC Electronic Flashback Triple Delay: $220 on eBay. This gives you 3 delays simultaneously. Most ambient players stack delays; it's important. A single delay pedal is OK, but you'll want another soon. (And then another!)
3) Reverb: Boss RV-6: $110. It's a workhorse with a lot of different reverb engines.
You still need patch cords to connect the pedals (preferably not cheap-o jobs). And you need clean power. Hopefully some of the pedals come with a separate power cord. Beware of the daisy-chain power. Down the road, you're going to want some kind of looper. I use the Boss RC-300, but it's expensive ($450). You can get a looper for under $100; look for Ditto. It will never end.