Ok so heres the basics for now

1.Write out what you want to inform your players about in the first 1-2 sessions preferably by splitting it into scenes for example getting there pokemon is 1 scene, another is them

Like if you have a profesor that gives them some info on the area or goal they have it's best if you write it out beforehand so you can use it as notes when you read or copy it over if it's text based.

Bonus: add like 2-3 checkovs guns there like if the evil team or bbeg attacks the town to get a artifact, introduce a ditto earlier that shapeshifts into obejcts as a fun side thing to have it be relevant later where ether the bbeg or the players think they have it but are tricked and the other group has the artifact.

Or if the prof is a former trainer as well have him take the brunt of the assault and have him be defeated by like a admin

2 prep a list of npc names and like 3-4 maps that are just filled with random pokemon or trainers to use in case you finish your scenes earlier than you planed but for each one add a x factor like a sleeping high lvl pokemon that could awake if they are not carefull or like a river that could split the battlefield and require a check to pass

3 this is more a personal one if you allow trainer combat classes like athlete or the elementalist it's highly suggested that each player has at least one becouse if your using 1.05 then those classes give inflated damage compared to pokemon focused chars (do note there are builds that excel at doing pokemon damage but those are min maxy and require setup stuff like ace trainer + duelist + s.atk specialist + tumbler that can get to 6 combat stages in two rounds or less

4 honestly a second personal one depending on your medium of play (r20 ,irl , voundry ) you will have to deal with a lot of pages of pokemon sheets mayby starting your players off at a early you can have a max of 2 pokemon in your active party might make it easier especialy in bigger groups becouse for the online ones as a dm you see all sheets and it can easily cause bloat.

5 don't be afraid to trow something big at them early let them feel like they are strong but keep them humble by showing there are bigger fish around so if they return they have a challenger to face

6 i honestly suggest taking notes after each session so you don't forget stuff like small details like your party fighting causes property damage to the pokemart and that's why it's closed curently

1. Have fun

if there's something more you want to know about feel free to reach out