That I didn't understand anything at all lol. I didn't know Pokemon boxes existed and I barely used any other pokemon other than my starter. My cousin helped me a lot with many things from the gym to the League which was impossible to beat for me. I only used Empoleon for my whole run and he was also my HM slave lol. He had: cut, strength, surf and waterfall. I used to always overuse Surf lol. The rest of the team was: bibarel, abra, staraptor and some random others but they were all under level 40. I remember I didn't like using items and also I didn't save before the battles, so I lost many many times and I attempted the League idek how many times, like 40 maybe lol. My Empoleon eventually arrived to level 100 doing that, but without items there was no way he could make it past Lucian. So my cousin helped me and traded me a level 100 Charizard and a level 100 Meganium and he easily beat the League.
Bonus things: as soon I got to know what Day Care was, I left my zubat there and I forgot it there for my whole adventure and when I got it back it was up of like 40/50 levels lol. I also remember that Uxie didn't spawn in the cavern for no reason or maybe someone killed it not telling me. Once, I notice a PC in the pokemon center, after the League, and I find out about boxes. And I could finally get Dialga lol. Then well, I loved the game and i lost so much time playing with friends, exploring the Underground and the contests. I have like over 300 hours on my old Pokemon Diamond file lol.
Is there a pokemon you particularly became attached to?