Who knows if any of this is accurate but I like this kind of upbringing/origin story for him.

Gibeon grew up in a very strict, wealthy household. His parents were both scientists/researchers, and he was expected to follow in their footsteps. However, his real passion was researching Pokemon, while his parents focused on researching people.

From a young age, Gibeon was fascinated by the idea of Rakua: a paradise he read about in stories. His parents dismissed it as a fairy tale, but Gibeon was convinced there was some truth to it, since, in his mind, it showed up far too frequently to be entirely fiction.

After looking through all the books he could find in both his home (I imagine his parents had lots of books) and local libraries, Gibeon compiled a list of evidence that Rakua existed, along with what he could figure out about its potential location.

During one of his visits to a library, he discovered a Zygarde cell. He'd read about Zygarde, so he knew more or less what the cell was, and he decided to take it with him -- hiding it from his parents.

Gibeon's parents were often at work, so it was easy for him to secretly pack up his things (or at least his essentials) and leave home undetected. His first goal was locating more Zygarde cells.

Once he had Zygarde, it would be much easier for him to reach Rakua.

Finding enough Zygarde cells to restore the Pokemon to its 10% Forme took quite a while, and Gibeon was growing concerned that he was putting off finding Rakua for too long. But he hadn't come across any other information, despite searching many cities and towns in his travels.

Eventually, Zygarde was able to regain enough cells to transform into its 50% Forme. Gibeon decided that Zygarde was more than strong enough to be of use on his journey to find Rakua, so he shifted his focus to that.

But he found it fun to battle with Zygarde, too...

Gibeon slowly gathered bits and pieces of information on Rakua as he went from place to place with Zygarde.

Until, one day, he happened to be in a cafe where he overheard two other travellers talking about the very place he himself was searching for...