In my (limited) experience with DA cards enabling Gardens, I'd like to share a couple of anecdotal stories of me getting crushed.
First, Squire/Gardens is most definitely a thing. My opponent opened Develop/Develop and got like 4 of those before going nuts with Squires and Gardens, which I don't know if it helped, but I got whomped that game.
Second, in a Beggar/Gardens mirror, any opening other than double Beggar just lost tempo. You get Beggars on 2/3 until you have 3 or 4 of them, then you get Gardens. Seems pretty typical for Gardens to run, then Coppers, then something else -- Estates or Beggars.