we don't have to spend much money on toys for our cats...
electra (2yrs) - she loves crumpled paper balls, aluminum foil balls, rolls of toilet paper, rubber bands, and she's very good at catching flies and she ends up playing with them .. so gross
antigone (4 mo) - she loves playing with her tail and electra's tail, a little red sparkly pompom, and pens/pencils/highlighters.. especially when I'm using them
I made a couple of toy mice outta fabric and stuffed them with batting and they've got a long string for a tail, and I made catnip pillows too.
they basically like playing with anything that moves, rolls on the floor, or makes a crinkly sound. they're very low maintenance cats!