Dry hamster food is very cheap, usually only about two or three pounds for a decent-sized bag. Which hamster food you choose to buy is up to you - do you want something that provides all the vitamins and minerals your hamster needs, or are you happy supplying fresh food more often in order to supplement the dry?
Hamster food is relatively cheap, and they only require small amounts
You may want to be a bit cautious if you choose to purchase loose foods. Make sure that it has been kept in a very clean area, as any moisture or dirt can contaminate the food with bacteria and mould, both of which can be very dangerous to your pet. It’s often best if loose foods in shops are kept in airtight containers.