Luggage and bags:
ok make sure you have a bag that zips for starters - not that i would say Chester is a thieves hotspot but better to be safe than sorry!
Clothing/Shoes/Weather Gear: It always rains....when you least expect it so an umbrella is a must. You also need flat comfortable shoes. There are many cobbled streets in Chester and wearing heels is not a good idea...you may get away with wedges but stick to something comfortable and flat if I was you!
Toiletries and Medical Supplies: you can get whatever you need here so don't worry if you forget anything!
Photo Equipment: again can pretty much get what you want here.