I have a radio control mouse that Waffles loves to chase...

.... also, my OH got an old cardboard box, cut a hole in it for a door, cut strips out of the other side and hung toys above it so that she can stick her paws through. He also made a kind of maze inside using other bits of cardboard.... really cheap and she seems to like it.

I also made a toy with an old toilet roll. I cut a hole in it, sealed the end and put treats inside.... was fun watching her trying to get the treats out.... that was until it all landed in her water bowl and went soggy....