C/G is fairly common for Anglos. It's probably a good "starter" box, but you'll find it fairly restrictive after a while - with just two rows, the "base" keys and their respective minors are just about all you can play in. That'll work for some songs, but for others, it'll be too high or too low for comfort. That's when you'll start wishing you had the extra row, with eg C# for the key of D, or Bb for the key of F.
Basic principle - get the best box you can afford. Or be prepared to trade up soon. But get one, and persevere - the world can't have too many concertina players!!

Andrew