Island/Gardens rush, hiding all your Gardens away on Islands, then just keep Ratting it up. If you empty the whole pile, each Gardens will be... 2 VP each... but it seems like a sensible rush.
Doesn't sound sensible to me without support. The Rats should interfere with your ability to buy $4 cards pretty quickly.
And it doesn't sound like a RUSH to me at all. It will take you a zillion turns to get all those gardens and islands, and by a zillion, I mean at least 17, and more likely somewhere around 20, at least if you want to get the things islanded away. And you need at least one more turn to get a rats, and probably several more really, because you can't actually start getting rats until late, because they'll choke you to death. Though your gardens are going to be worth 3 there, so hey, that's something. But not near enough to beat, say, BMU+island, I would guess (even though that speeds you up).
Though, hey, it is sorta cool, if you get 2 rats and no cards in your deck (i.e. you've drawn them all), you CAN gain the whole pile at once: play a rats, draw nothing, get an action, gain a rats, (can't trash a rats, so at least you still have that); play a rats, draw the rats, get an action, gain a rats, can't trash rats, rinse and repeat.