but as a collector, shouldn't he be focused on every rare Pokemon? The events of movie 2 likely just focused on his campaign to capture Lugia, whom also just happened to be his first of what would've been many targets (and don't forget, he started out with a Mew card... probably because the card in question is rare, but he could also have an obsession with that Pokemon). One should also keep in mind that, back when movie 2 was released, the idea of collecting every Pokemon was a far more feasible task (even in spite of the advent of generation 2 prepared to add 100 more), and it especially helps to remember that there were only 5 legendaries in generation 1, with Lugia making 6 (Houou's 7 if you wanna count its appearance in the first episode).And Jiri has no interest in having any other than his fixation on Lugia, but that's canon.
Actually this can be done effectively. I'll use your example with Feebas. The character longs to have a Feebas, but they live nearby a volcano with no bodies of water anywhere close to it. This way you can give them almost all Fire Pokemon and still have them want the Feebas.3) Look at the character's goals. Someone mentioned a thief having ghost and flying and that's a pretty good example. Example of what not to do: give mostly fire pokémon to someone who's ultimate goal is to catch a Feebas.