You need at least 2ft long (60cm/600mm long) x 1ft/30cm/300mm wide tank for one axolotl. Axolotls use floor space rather than height. Too small a tank and your tankwater will foul pretty fast and water temperature heats up faster which can make your axolotl sick.
Another thing you'll have to be aware of is if your axolotl gets sick, you don't use fish medicine as they can be toxic to an axie, and usually the best place for an axie to recuperate is in a container of dechlorinated water in the fridge (as long as temp is above 4degrees celcius).
Axolotls don't need company.
No gravel/pebbles are needed. You can have a bare floor tank which is easy to clean
No animals/fish for feeding.
check out:
www.axolotl.org
Before getting an axolotl I'd advise you to cycle the tank before buying an axolotl. see:
http://www.caudata.org/cc/articles/cyclingEDK.shtml
Any questions ask.
Other items that you'll need will be :
freshwater test kits to test water quality while cycling. (you can get individual ones for ammonia, nitrite and nitrate or buy a Master test kits that have all the test kits for the 3 mentioned as well as low and high pH).
water ager/dechlorinater/conditioner (to treat tapwater to remove chlorine and chloramines)
turkey baster (handy for daily spot cleaning - removal of poo/uneaten food/waste)
Siphon gravel vacuum (for waterchanges)
Thermometer (to monitor temperature - best temperature is below 20C)
buckets (if you don't have any for waterchanges)
No other chemical is needed. So if the petshop/aquarium advises you to buy something that isn't mentioned - don't buy it. Check with this forum and someone will help.
Axolotls can be fed on pellets, earthworms, frozen bloodworm cube. They don't generally eat anything that floats at the top of the tank (ie flakes). Don't feed them on dried tubifex cubes they just float and disintegrate into a mess in your tank.