Create a new products list

Hi, I have just set up an Amazon Sellers account and want to start creating my product list on but am not sure where to start as it suggests using codes such as UPC, EAN, ISBN & ASIN,. As I make personalized handmade hampers/nappy cakes which include numerous items, does anyone know how I can list these hampers using one code? As my hampers also vary in contents is there codes I can use for different categories? Please could anyone advise me? Thanks Heartfelt Hampers