There's not really any skill to them. You follow the instructions to hook them over the top of your monitor, you run some wizard-based software and it spits out a colour profile and asks if you want to set your OS to use that profile by default.
You don't have to buy the colorimeter at the same time as the monitor though; Get a monitor, manually adjust it to your liking, with the assistance of sites like lagom.nl
and then see how good it is to work on.
If you notice that colours are off you can usually get halfway towards a calibrated display just by manually tweaking it whilst comparing to another display that has a known colour accuracy. Find a half-decent display that you have access to from this list
and adjust your display as best you can to match the phone display. If the phone display isn't perfect, at least that site will detail the limitations of that display, so you can mentally adjust when matching your display to the phone if you know that the phone is cooler (bluer) than the full sRGB gamut.
You could always try using a smartphone as a ghetto colorimiter, though it'll be limited to the accuracy of the camera in the phone. COLOR GRAB and CAMERA COLORIMETER are two apps that look promising but I've used neither so can't comment on how well they work. Failing that, even a budget colorimeter is a good investment if you're actually trying to produce colour-accurate work. Sypders aren't too expensive (just over $100) though you'll need to buy a patch card to get the best out of them (another $50).