this is a oc pokemon challenge you have to write your trainers journey from start to finish from getting their starter to when they end it if you want to do an ash story he can't be his usual dumb ass self
for pairings if you do an oc trainer you can do what you want pair him with another oc or with someone from anime or manga or wherever you want but there is one guideline for both they and ash it can't be misty or a pokemon that shit's weird and childhood destroying
for their starter pokemon it has to be one of the 4 3 stage psychic pokemon that are out so far if another comes put by the time you take this challenge they you can use that as well they are
The Abra line Abra, Kadabra and Alakazam
The Ralts line Ralts, Kirlia and Gardevoir or Gallade
The Gothita line Gothita, Gothorita and Gothitelle
The Solosis line Solosis, Duosion, and Reuniclus
also you can give them mega evolution if you please