I use timers on all of my lights, just keep cutting back (slowly) untill you can see your plants suffering, then you know the min. light required. Also in fish only I put the lights on when I'm home.
Whenever I need to buy something for the tanks I try to sell something else to get the money. For example, I recently wanted some new plants so first I sold a few live food cultures and ended up breaking even. I keep several wads of moss growing all the time in case I need to sell it off. I don't always get all my money back but it really helps.
Join an aquarium club. I once bought 6 young Neolamprologous multifasciatus at auction for $1! I took 3 of them into the store I worked at and got $2 a piece for them. Deals on equiptment can be just s good.