Cheap Macro lens for A57

Might I add that you could try this alternative.
I spend $10 on a set of macro extension tubes, $3 on a reverse mount ring and $5 on an old Minolta 50mm f1.7, all on eBay.
I've also bought a 28mm which should get even better results, but I'm still waiting for the reverse mount ring for that lens.
If you'd like to play around first with macro, this is a cheap option.
Of course if you'd like to get more serious, there are some excellent tips in all the other comments.

camera: a77
ISO: 100
speed: 1/200
lens: reversed 50mm at f11 with macro extension tubes.