Now you might want to confirm this elsewhere, but from what I know, mirrors are actually going to eat your light more than reflect it! I thought about mirrors, then looked and saw that it wasn't going to do any good at all, and can in fact lower your total light that gets to the plants.well picked up a mirror today i can use a mirror instead of like foil cant i for reflecting light
I'm all about the poor man's grow, though. My poor lady grow has turned into a much more expensive operation, but think of the money you'll save on bud once you get your growing skills down Y splitters would be a fantastic investment, $2 at Home Depot. What i used for the lighting is these 'bottle lamp' kits, $4/piece at Walmart and they work just fine.
If you start having problems like yellowing, drying leaves, spots, etc. you might want to invest in better soil. I was stingy with soil and got miracle grow, but my plants were not so happy about that. It was well worth it to pay $17 for a bag of Fox Farms soil.. especially considering I spent about $14 on all the miracle grow soil.