Just buy what you want. I have done the mix pack before and don't recommend it. Not this mix pack but from other vendors.
They do not put the good seeds in a mix pack.
I know having a bunch of different strains for cheap sounds amazing but in the end it is just a head ache going the mix pack way.
Just find several amazing genetics you want and pay the piper.
My 2 cent
Growing is easier when you know what you got. Some strains are hungry and others not so much.