A waxy potato, well my favourites would have to be Charlotte, largely grown as a salad variety, but gorgeous if eaten in just about any way !
Cat : I'd not bothe rincorporating bagged materials unless you have no other option - if possible start your own home composting system, that works brilliantly and does not cost a penny, you could also use compost taken from seasonal containers etc, then add some general fertiliser or some well rotted manure to increase the nutrient content.