i am going to buy a tank in the next few weeks, right now im set about 20 gallons. this tank will be fresh water and i want to have plants as well as fish. my questions are: is there a tank dimension that is more popular or cheaper to find lights for in this size? what are some good brands/types of filters (as reasonably priced as possible, with good quality components)? is making my own filter a reasonable idea for a tank this small? what brands/types of lighting are best for light/fish combos? i found a tank that has similar dimensions WxD, but is considerably taller than the others. i think it was the same dimension as a 20 gal, but twice as tall. is this wasted space for my fish and plants? my hope is to get a tank from craigslist or used and build from that, but i may go new. i would rather get it sooner than later but am more worried about cost of startup. any ideas or suggestions are greatly appreciated.

What size tank are you looking for as far as the footprint goes

i have plenty of room, and an oversized table that i will use for the stand. what i really want is the best buy and the easiest to find good quality parts ie lighting for

Once you get over like 20 gallons you really should be useing an Aquarium stand because they will have the proper support directly under the tank. I would go with something closer to a 50-65 gallon breeder because anything smaller you will be very limited on the fish you can keep in it and the bigger you go (at least to a point) the easier they are to take care of