If you plan to visit Maiden Castle, you should take some good walking shoes. Sneakers are fine, you don't need real hiking shoes, but it would not be good to walk around Maiden Castle wearing sandals, flip-flops, high heels or similar. The ground is very uneven and slippery, and sometimes you need to climb a little in order to get onto the earth embankments. The same goes for Maumbury Rings.
Even if you are not going to these place, it might be good to wear very comfortable shoes - Dorchester was much bigger than I had expected and I walked much more than I had thought I would.
Luggage and bags:
Luggage with wheels is always a good idea, wherever you are travelling.
Clothing/Shoes/Weather Gear: Whether snowy/wet/sunny/warm or cold weather, layer your clothing.
Wear thermal underwear (these are easily bought at the local clothing shops), with warm leggings and a top under a toasty jacket for the cold. I have my trusty grey duffle coat, plus a white snow jacket for this type of weather, and they are a godsend!
Wear flat shoes that have a good grip, as when it is snowing, and afterwards, when it is sludge, it's really difficult to walk and keep your balance!
Always remember to bring a cap/hat that covers your head and neck for when it gets hot, as well as sunglasses.
Toiletries and Medical Supplies: Sunscreen (Factor 35 is the minimum factor I use, no matter what the weather is), headache tablets and usual little things like some plasters for blisters, cotton wool, germolene etc.
Photo Equipment: Your camera, with charger, and a EUROPEAN plug extension.
Miscellaneous: Have a map of the area handy, plus a local bird, flower and tree book. For this you also need a pair of good quality binoculars