Walk through the colored-pencil aisle of an art store and you'd be forgiven for thinking successful coloring requires several hundred dollars' worth of equipment. It doesn't.
A decent set of colored pencils, paper you enjoy working on, a reliable sharpener, and an eraser will take you surprisingly far. Everything else—blenders, specialty erasers, pencil extenders, storage systems and assorted mysterious little implements—can be useful, but they're additions rather than admission tickets.
The best tools are the ones that make coloring easier or more enjoyable for you. Start simply. Add things when you discover an actual reason you need them.
If you're putting together your first coloring setup, I'd begin with just a few essentials.
Colored pencils: You don't need the largest set available. A smaller collection with a good range of light, medium and dark colors is plenty for learning layering, blending and shading. Don't go cheap though. A mid-grade pencil will give a decent result, whereas a cheap pencil will leave you thinking you're doing something wrong. Buy a single pencil in a couple different grades to compare.
A sharpener: Probably more important than people expect. Fine details, fur, hair and crisp edges are considerably easier with a properly sharpened pencil.
An eraser: Colored pencil doesn't erase like graphite, but an eraser can still lift pigment, soften an area or rescue a highlight. A kneaded eraser is particularly handy, and we'll give that peculiar little lump of putty its own lesson.
Scrap paper: Keep a piece beside you while you color. Test combinations, pressure and blending there before committing them to your page.
Good lighting: Not glamorous, but important. Poor lighting can make colors look surprisingly different—and makes seeing fine details unnecessarily difficult.
Once you've been coloring for a while, you may want to experiment with colorless blending pencils, white pencils for blending and highlights, pencil extenders for those beloved colors you've sharpened down to tiny stubs, and different types of paper if you're printing your own pages.
But don't assume that owning a specialized tool means you have to use it. Some colorists love colorless blenders; others barely touch them. Some keep elaborate swatch charts. Others grab whichever green looks promising and carry on.
Both camps somehow survive.
Make a tool test page.
Take a coloring page you don't mind experimenting on—or simply draw several circles, leaves and rectangles on scrap paper. Try your pencils with light and heavy pressure. Layer several colors. Test your eraser. Try your white pencil over another color. Compare a sharp point with a blunt one.
You'll quickly discover where your current supplies work beautifully and where they're actually limiting you.
That's the point at which another tool becomes useful rather than merely tempting.
Upgrade because you've discovered a limitation—not because somebody else's art table has more stuff on it.
A modest collection of tools you understand will usually serve you better than a drawer full of supplies you haven't learned to use.