My first was Yellow. I was terrible, it took me ages to figure out I had to leave Pallet Town to find Prof. Oak. And even then, I went through the entire game without realising I could change the order of Pokemon in my team. My Pikachu was like level 70 my beating the league and the rest were like level 5.
I also remember calculating how power a move was based on its PP. The less, the better. To be fair, there wasn't much information they told you before you taught a Pokemon a move. And I thought all non-damaging moves were useless.
It took me even longer to find out how the stats work. And how types worked. And even longer again to learn that STAB isn't all that important.
But hey, I was young.