Drum sets can come with a different sizes of individual drums, (mostly length differs as the width is more standardized, more about that later), colors, hardware configurations, a set of cymbals and can range from 2 drums, all the way to 20 or more drums in a single set, and can cost between $100 to $20.000 and more.
The most popular drum kit configurations are the 5 piece and the 8 piece sets. The typical 5 piece drum set consists of 1 snare drum, 1 bass drum, 1 floor tom, and 2 rack toms, while the 8 piece usually contain 1 snare drum, 2 bass drums, 1 floor tom and 4 rack toms. (9 piece drum sets are usually configured by adding another floor tom to an 8 piece drum set).
But those are the "standard" or better yet, "the most common" sets, in reality professional drum kits can demonstrate many, many different setups like 2 snare drums, 1 rack tom, 1 bass drum and 2 floor toms, or 1 snare drum, 2 bass drums, 2 rack toms and 2 floor toms and so on...
Who's got the "Big One" and who has a "Small One"
There are some things we the drummers need to consider when choosing our X drum set configuration, the individual drum sizes and hardware. Aspects such as transportation and setup (one of the most important). The actual set configuration (this one should come before anything), one should always ask: "Is that enough for me?" or "Do I really need a set that big?" It is always better to (at least) have an idea of what you are looking fore prior getting your self to a drum store ready to make that purchase! Among other important things to consider are the actual producer of the set, the price range you wish to spend on your drum kit, the "looks" or the actual color or finish of the drums, the warranty, and the endorsements.
Transportation and Setup
While some of the drummers do prefer bigger drum sets (8 piece and up), with massive and heavy hardware, transportation and setup time should be the main decisive subjects, and if you really don't have 5 roadies to help you carry your set out of the truck and set it up on the stage, you should seriously consider having a smaller setup. - Isn't the main subjective to be able to set your kit on the gig in time and without "killing your self" prior the gig while doing that?
Hardware and drum set configurations
Most drum manufacturers provide their sets with cymbals and basic hardware while others just sell drums that don't come with any stands or may even don't include a snare in a typical drum set. (that is true with some of the biggest producers of professional "top of the line" drums, like DW for example). One should carefully examine what really comes with a particular set, along with the quality of the hardware and or cymbals and the manufacturers warranty.
The great looks
The actual finish of the hardware and the drums is perhaps one of the least important factors that influence the overall value of any drum set, and because of that you should simply go with the finish or color that will rock your world the most! - Also don't forget to get yourself drum cases or at least covers for all your drums, to insure that the outstanding drum finish you chose - will stay outstanding for a long time!