for starters you need 6 things: tank, heater(if keeping tropicals), filter/water mover, light, stand and stuff to make waterchanges easyer.
if you find a used tank, ask how it has been stored. if it has been in the sun much don't get it as the silicone deteriorates badly if it has been outside for any length of time. Kit tanks and cheaper versions will hold water, but the silicone isn't done neatly, or the top rim might not be even. It is up to you what quality level you want.
Do not skimp on the heater. Buy the most reliable brand you can find as failure often means cooked fish. I wouldn't trust the heaters in a typical kit.
Just about any thing that moves water will do the job in your tank. All require some sort of mantenance or cleaning. Some are quieter, more reliable than others but they all work. Undergravels are considered old school and outdated, but if that is what you can afford they are useable.
the most versatile top I know of is plain glass with a plastic hinge down the middle. any light works over that and if you decide to grow plants adding more light isn't hard.
I am currently building a stand for a 29 gallon tank. $20 bought the 2x4s, screws, and a driver bit for the drill. I plan on spending more to finish it up so it looks nice, but will support the tank on just what I have now.
I have a few of the particle board stands. No real problems from them, but my peace of mind says I want a material that doesn't fall apart when it gets wet so I am working on replaceing those.
All the actuall cleaning gets done when water changes are made. Filters make the water clear, water changes make it clean.
Cheap route is a bucket and siphon with a larger gravel vaccuming end on it. Less hassle is a special hose to drain and fill your tank. Python is one brand, and you can make one out of a waterbed filling valve and foodgrade hose.
