shhh, don't tell anyone ;D
we grew dried peas from the supermarket, got peas that were a bit marrowfatty, we used supermarket spuds that had sprouted, in containers..seed from tomatoes, peppers, chillies and squash that you buy can be dried and grown..also, we've done fennel and celery from seed for cooking..don't know how well they do, didn't keep notes then
lidl, netto, aldi, wilkinsons all have seeds at less than 50p in spring..keep a watch out on bargains galore on this site :)