Good points for the differences, even a couple I was not aware of - thanks!
As for the kit to start with, try to find the Monogram ProModeller kit of the 109G-4 It is the Hasegawa kit and comes with a set of suitable resin wheels, although I'd recommend the AIRES Bf.109F wheel set myself, especially as it comes with a suitable tail wheel for the earlier 109's. I believe Hannants and possibly Squadron have these in stock.
Squadron had these kits on sale for $20 (I've got 4 myself and am using spare parts from my other 109 kits to convert these into later variants, but to do a G-2, this is perfect for you!