The tank is light tight. The film is rolled onto a reel which is a spiral that keeps a space between the layers of film, so the developing solutions can flow evenly onto the surface of the emulsion. The bottle opener is used to pop the top on the 35mm cassette. The scissors are necessary to cut the film leader before loading film onto the reel. An accurate darkroom thermometer is extremely important because the length of the development time is determined by the temperature of the chemicals, and for proper processing all the developing chemicals need to be at the same temperature. You will also need as many measuring beakers as there are steps in the particular developing process you are using, according to Andrew Gibson.
It is important to have an accurate way of timing each step in development. A timer that lets you program in several steps is best. The chemicals needed will depend on the type of film you want to process.
I suggest starting with black-and-white film because it is the most forgiving and many times can be done at room temperature. Black-and-white film development uses three chemicals: developer, stop bath and fix.