Well, I expect Lugia's team to be the one encountering more dangerous opponents. You may wish to pick up a couple of defensive mechanisms at the very least! You're free to come up with your own interpretation of his abilities, but the maximum breadth of a pokemon's magic is typically derived from something resembling the movelist. Espurr has access to many electrical attacks, which implies the potential in our setting to attune to such magic. It won't be as strong as that of our ampharos, most likely, but the option is certainly there!
The most efficient and natural option for most espurr would of course be to practice their psychic powers - be that to toy with a victim's mind or to overtly force one's will onto the natural world.
Give some thought to the character's mindset and how he would approach magic. Is he a generalist, who likes to dabble in a bit of everything and spread his capabilities as far as he's able? Does he seek to master one very specific power - the ability to trap his enemies in a mental prison, or to overcome reality with sheer force of will? Or does he lie somewhere in between, practicing which key spells matter to him to shore up his weaknesses?
Edit: An addendum. I mean it when I say "typically" - if you want to do something outside what you would think is possible, don't be afraid to ask. Just be prepared to explain how it works. Feuertanz already does this with his quasi-healing magic.