well idealy you want to be learning with the styles of music you are into, sure learning how to beatmatch will probobly be simplified with 2 simple dance tracks but your not learning anything other then beatmatching there.

i say if your around your mates or something then have a little practise with there music but at home stick to the music you want to mix for if you get me, as that way you will be picking up the beatmatching skills you need but at the same time learning how to bring together the music you are into and how to structure your sets etc :).