I'm a semi-serious player.
I aim to catch good-natured pokemon, and I generally plan my team ahead of time, for balance's sake. I train in increments, usually 2 or 3, and rarely deviate. I use the best movesets I can and aim for good coverage on all pokemon. I try to use each and every pokemon in a region in repeated playthroughs. I don't EV train, and I don't breed in story mode. Post game, and competitively?
HARDCORE, BABY.
In my pokemon Diamond game, I have 440/493 in my pokedex, and about 320 caught. I have 5 different boxes full of Lv. 50, somewhat EV trained competitively viable pokemon that I use in the battle tower, against friends, and occasionally on Wifi. I used to battle competitively over Shoddy Battle and Pokemon Online, but my community died, so I haven't done so since about 2011.