That's a pretty subjective question. If you're looking for opinions, I'll give you mine for what it's worth...
I definitely like gaming mice. I recently upgraded from a cheap one to a Logitech G500 and wish I'd done it years ago. It feels much nicer, slides much more consistently and the adjustable dpi is handy.
I got a keyboard a couple of years ago. Again, I subjectively like the feel of it much more, though unlike the mouse I can't say it's helped my gaming at all. I imagine if you're an MMO player or are into programming macros, the additional keys offered on some keyboards could make a massive difference. That's not me. I do a looooot of typing however, and the mechanical keys are great (again - subjective!). While at...