Goody goody gumdrops, I love dispensing knowledge about games I enjoy.

The weapons you choose at the beginning determine your stat growth and the order in which you learn abilities. The rod enhances your MP, the shield enhances your defense, and the sword enhances your attack, basically.

The White Mushrooms are the cute little guys who don't attack, but play charades instead. If they shiver, cast Fire on them. If they fan themselves like they're hot, cas Blizzard. If they look lethargic with a light over their head, cast Thunder. If they spin around, cast Aero. If they float, cast Gravity. If they freeze, cast Stop. And finally, if they collapse, cast Cure. Cast the same spell on them three times to get the Fire/Blizzard/Thunder/Aero/Stop/Gravity/Cure Arts items (among other things) which can be turned in to Merlin once you get one of each for a new item, and sell the rest. Don't attack them, because they are one of the few Heartless in the game who don't try to wipe you from the face of the universe.