Pokemon cards (De Parys MK40)

My son has come across a few cards and loves the idea of now having a "collection". He has no idea how to play properly with them - this morning was just arranging them from cutest to stinkiest. I'd rather not start buying him sets of cards, but if anyone has a few duplicates they don't need that would be great. Apologies if this is something for buying & selling rather than giving, I don't really have any more idea about them than he does.