Water: The most crucial thing if you are going to go far is that the dog has access to water. So take a container of water with you on the trip and possibly a bowl to drink from.
Food: If you are going far, bring some food for the trip. A dog uses more energy than usual when it has to walk far. Also, bring a chew or something similar for when you take a break to keep the dog calm.
Tick repellent: Dogs attract ticks like magnets. If you are going for a long walk or going into the woods, consider drenching the dog with tick repellent before the walk.
Two leads: It can be a useful to bring a short and a long lead. The short lead should be used in towns, as well as places where there are many people or traffic. The long lead is for when the dog can be a little freer.
There is plenty of gear and equipment you can bring on the trip, such as bags so the dog can carry the equipment itself, but this is rarely necessary. However, if you regularly go for long walks, a dog first aid kit should be included in your trip. Dogs can get hurt, and their paws are particularly vulnerable.