You COULD buy 2 xEM or you SHOULD just buy 1 xEM (I Still reccomend the NExT) and just grab a cheap card off, amazon, ebay, aliexpress etc. to test/ practice on.
My Proxmark actually came with a T5577 card…
HERE is a very helpful guide @TomHarkness answered somebody in a similar situation.
and hopefully THIS wiki is of some use to you.