I'm gonna only half-agree with ptoing here;
Perfect screen calibration is indeed overkill most of the time (as was said, unless you're printing). However, from personal experience, you want to make sure your screen is "okay"; every screen will show things differently, but if yours is badly calibrated...
Let's say that with a good screen, your work will "on average" look better on other's.
Like, if your screen is too dark, you're likely to make brighter stuff, and end up with more people seeing it too bright.
Does that make sense? XD
Either way, make sure you buy a somewhat decent screen, and look up for websites for screen calibrating, usually that should be more than enough.
Buying a physical, hardware calibration probe thing is a waste of money.
Also, I've never used it myself, but I know some websites provide preset or calibrating softwares/drivers for the most popular screens, you might want to look into this!
Most screen come with far-from-perfect settings, and can easily be tweaked to give a much better image.