Well, he might turn the land into a large garden filled with magical plants. These plants could be used for potions, or just to beautify the area and attract friendly magical insects and animals.
He could use it to build a magical sanctuary for endangered magical creatures. This would be a place where they could live and breed safely, away from the threats they face in the wizarding world.
Perhaps he'd use the land to establish a school for young witches and wizards who don't fit into the traditional Hogwarts model. A place where they can learn magic in a more personalized way.
Well, it could be about Harry and his friends having to journey into the Land of the Dead to retrieve a powerful magical artifact. Maybe they need it to defeat a new dark wizard who is using the power of the dead to gain strength.
It could be a powerful dark wizard who has found a way to control the forces in the Land of the Dead. Maybe he was once a student at Hogwarts who delved too deep into the Dark Arts and now wants to use the power of the dead to rule the wizarding world.
One possibility is that Harry is exploring the Muggle world more and decides to buy Grunnings out of curiosity. Maybe he wants to understand his uncle Vernon's world better. He could use magic in secret to improve the business operations and make it a more efficient place, all while keeping the Muggles there oblivious to the magic involved.
In this fanfiction, Harry Potter might be facing a new situation in the Muggle world. Buying a car could be a sign of his further integration into Muggle society. Maybe he uses his wizard money to buy a really cool and unique car, like a classic convertible.
Well, perhaps Harry, tired of the wizarding world's chaos, decides to buy an island for some peace. He could use magic to build a unique, hidden mansion there. Maybe he'd invite his closest friends like Hermione and Ron to visit, and they'd have magical adventures on the island that are different from those in Hogwarts.
Well, he might choose a house in a wizarding village. Maybe it's a small cottage with a charmed garden full of magical plants. He could use his Triwizard Tournament winnings to pay for it.
Maybe Harry Potter, after all his adventures, decides he needs a peaceful place. He uses his wizarding money to buy an island. He might turn it into a magical sanctuary for magical creatures, away from the prying eyes of Muggles.
Maybe he has a specific mission. For instance, he discovers that there is some hidden magical power or artifact on Lord Stark's land. By buying the land, he can explore and protect it without interference. Also, it could be a strategic move to expand the influence of the wizarding world in a non - traditional area.
It could also be a strategic move. Gringotts is a highly secure place. By buying it, Harry could ensure the safety of important magical artifacts or secrets. He could use it as a base to store and protect things that are crucial for the future of the wizarding world, like ancient spells or prophecies.
Ron might be there too. He could use his skills in handling magical creatures to populate the island with friendly ones. And he could also help with fishing in the surrounding waters using magic, providing food for those on the island.