Please be prepared as Belgium weather can be very unpredictable. It is possible to have all types of weather and nights can be cold.
Comfortable backpack or trolley
Hiking shoes or comfortable trail shoes
Sneakers
Slippers for indoor (optional)
Comfortable clothes for hiking
Hat, gloves and suncap or headscarf
Warm clothes for in the evenings
Water bottle
A small daypack is useful but not obliged
Headtorch with needed batteries
Personal hygiene: toothbrush, soap, towel
Personal medication
Bring something typical from your home country to eat