In Divinity: Original Sin 2 players are literally overflown with hundreds of items of varied usefulness. However, there are two without which the game is much more difficult. Those items are a shovel and a bedroll. A shovel allows you to dig up hidden treasures or reveal secret passages that lead to additional quests and/or characters. A bedroll allows the entire team to get back all their health points and both types of armor as well as remove all negative statuses (besides the permanent ones). In addition to that all characters get a buff that gives them +1 to Strength, Constitution and Intelligence.
You can get these items in many places - you can buy them from merchants or simply steal them. However, players can find a shovel and a bedroll right after landing on the beach. When you regain control over your character you must head south (go past the place where The Red Prince stands) and then climb on ruins of a bridge (the more precise location is marked in the picture above). There, you can find the two items as well as a cooking pot that allows you to cook something (more information in "Crafting" chapter) and a few containers.
Bedrolls are worth using before (to strengthen your team) and after (to heal wounds) battles. As for shovels, the guide has maps of all key locations on which we marked all places where you can find hidden treasures. Simply go there and dig up a treasure - however, in order to detect them you need a character with well-developed Wits attribute.