What to look out for when buying a concertina:
Brand new doesn’t always mean better. Some of the best concertinas on the market are second hand and even antique.
On this site, and in Irish traditional music in general, we learn on the Anglo concertina. There are many systems, but if you want to learn Irish music, I recommend buying an anglo.
Try to get a 30-key (at least) concertina. This will give you more versatility than a 20-key concertina and you will be able to play everything on this site on a 30-key.
more reading: https://irishconcertinainformation.com
Concertina Sellers - Shops and makers