Firstly, I don't know what Plaza does except that it's a Village: I want to be surprised when I get Guilds so I only know the general characteristics and costs of the cards. Plaza probably has some cool effect other than being a Village that could possibly change my analysis.
The Ruins from Cultist without trashing makes multi-Goons turns pretty difficult to pull off.
Goons is always good, even more so with Scheme/Gardens since you can get more +Buys and +VPs from Goons by scheming it and more cards for Gardens from that. Also, because Goons is on the table, this game is probably going to end on piles.
I'd grab a Nomad Camp to start with, get Goons if I could later, and would ignore Cultist. I don't think Ruins hurt Gardens enough so much as activates them, and with a source of +Buy in Nomad Camp and Goons I don't think you'd be able to beat it, particularly if both other players go for Cultists.
I wouldn't transition into a Gardens strategy until someone commits with Cultist. Once someone does, the Gardens-split becomes very important if either of your opponents see it. If no one bites on Cultist, you'd probably want to go for as much an engine as you can with Scheme, Plaza, Treasury, and Goons. Managing a Nomad Camp/Treasury opening wouldn't be great for Gardens, but it could help some 3-card hands once the other players start throwing Goons around.
If both players go for Cultists, the Cultist pile will likely empty, so rushing the Gardens pile would be immediately important since that will be the third pile after the Ruins are handed out.