First off, there are two types of screwdrivers. Most people know this. They’re called the Phillips screwdriver, or the Phillips-head screwdriver, and the slot head screwdriver, also called the flathead or regular screwdriver. The Phillips screwdriver has a head shaped like an ‘x’. The regular flathead or slot head screwdriver is shaped as it’s name indicates - flat and rectangular. Anyone who uses screws should have both kinds of screwdrivers. If you only have a Phillips screwdriver, you’ll find yourself stuck when you come upon a screw designed for a flathead screwdriver.
Among the Phillips and flathead screwdrivers, there are different subtypes that can be used in different situations. For example, you can buy a short screwdriver if you work in cramped conditions. Or you could buy a heavy screwdriver if you deal with large screws. I’ve found that you should have a pretty wide variety since screws themselves come in a pretty wide variety. Of course, it depends on what job you have and what you think you’ll be working with. Just make sure you’re not one of those guys who strip screws or ruin their screwdrivers through misuse. Don’t use large screwdrivers for small screws, and never use a flathead screwdriver for a screw designed for a Phillips screwdriver!
This will get you started on using screwdrivers, both professionally and just for home use. Good luck and happy screwdriving!