Dave mallinson brought out several tutors for two row melodeon[diatonic accordion] [g d].
the gd two row is in my opinion the most versatile for playing in g d ,95 percent of irish tunes are in these or related modes.
it is the most versatile because,when you start to crossrow you have more notes on the push and pull that are the same,also it is easier to play the correct basses,lots of bc players struggle in d major.
when you are playing in a noisy pub a gd going with full basses,is wonderful its like a rock that everyone can hear,.
if you want to be fully chromatic a two and a half row is the answer,this is what Jim Bainbridge uses.