Oh man, gardens makes Amb play risky.
Still worth it with no +Buy and no gainers around. If they just take the junk and go gardens, get a YW and make their junk have 10 curses, and make a rabble engine so that each hand they have starts with 3 dead cards. But add the YW in later not at the start.
Amb/Silver/Amb seems plausible. Amb/Warehouse/Amb seems like it would kill your economy just a bit too much, and Amb/Warehouse/[no second amb] would probably lose to a double-amb? Maybe? If you got some good draws early, the Warehouse would let you play your one amb almost as often as a double amb opening? But man, A/W/A would win the amb war so hard.
Not sure. The priorities would be
1) Win amb war
2) Build MV/Rabble engine
3) Add a YW
4) Buy green, use warehouses to keep drawing your deck and your junk out
but I'm really not sure what sequence of Amb, MV, Silver, Warehouse buys are best for (1) and the transition to (2).