Using a water-soluble, or easily dissolved, cleanser and some muscle power goes a long way toward preventing odors in and around the toilet, and doing it often enough can keep smells away longer because there is less time for mold and gunk to form on top of other bacteria and junk. Once a week is probably enough for low-volume households, but if you have a family of six or share a house with four roommates, for instance, you may want to rotate bowl-cleaning duties a couple of times a week. No matter the household size, you can even do a quick wipe-down daily to avoid a more intensive cleaning later.
Adding disinfectants after cleaning (and being careful not to mix bleach with other chemicals) cuts down on the germ factors behind odors. Deodorizers also eliminate unwanted aromas by masking or neutralizing odors but don't do much, if anything in the way of cleaning. Some home plumbing systems have additional smells just because of the water source or system, such as septic tanks or well-water versus sewers, but neutralizers can help cut down on those as well.
Despite how it looks in advertising, having a clean and odor-free toilet takes a little work and some regular appointments with a toilet brush. If only it were as easy as dropping in a tablet, flushing up a tank of cool, blue water and seeing flowers float up from the bowl.