Questions about buying spare wheels

Hi everyone!

I’m signed up for my first race in June, and I’m trying to get all my ducks in a row ahead of time. I’m looking for a set of spare wheels, but since I’m probably going to get a whole new bike at some point next year, I don’t want to break the bank. Unfortunately, I’ve spent a whole lot of time working on my fitness, but not much time learning about bike mechanics, so i’m a little lost as I browse for wheels.

So, a few questions:

  1. would you ever buy wheels used? If I do, is there anything in particular I should look out for?

  2. what measurements do I need to verify that a wheel is compatible with my existing cassette and general set up?

  3. other than weight and material, is there anything in particular that differentiates a “nicer” tire?

My existing wheels are DT Axis 2.0 stock wheels off a 10 speed Allez (this one, in particular: Allez Comp Apex Mid-Compact |

Any resources for learning about this side of things would be helpful too. Thanks everybody!