I love games with alot of dialogues, so for my first nuubie hack, I am making lots of dialogues.
This inspiration comes from my own character, I love to talk and write stories, but I also had this inspiration by games like the Tales series and Golden Sun.
Pokémon lacked alot of dialogues with the main character talking him/herself.
Since I am a student myself, I implemented a school, and when you all graduate in the game, you're going on a big adventure. You will encounter your schoolfriends quite a lot of times, and you will get to know their (back)stories with time passing.
Further concepts and inspiration:
Usually the real world and the Asian continent.
One of my favourite concepts that I have yet to implement and to write down on paper (its in my head already xD) is a part of the region in war or in a truce. You can Pokemonstyle this to Korea somehow.
Also, back in the day I dreamt about Pokémon while I was asleep, I remember some of the dreams and I can work them out.
I also made routes and Gyms with LEGO and had those Pokemon dolls that you could buy at a local store, with a Pokeball. I combined these 2 things to play outside when I was young. As I started imagining stories with my friends back then, I still remember some of them to work out in an actual hack.
Mainly I will get my inspiration from things that happen(ed) in the real world, like the Korea part for e.g. I also mix real places' names and create my own, kinda what Golden Sun did (Dejima [island in Japan] became Idejima in Golden Sun) You only know it once you see it.