Quote Originally Posted by Joshkabob
Where do I buy stuff? And change classes?
Like MSchmidtt said, once you have some money you can buy some equipment in towns (those are the white dots on the world map), I would strongly suggest stocking up on potions(10 or 15) and phoenix downs(5 to 10) at first. Fight a lot of random battles before advancing the story too much, thus you can get plenty of money, equipment, and JP for buying skills.
As for changing classes, when you press the triangle button on the world map, it will bring up a little screen... select 'Formation' to get a look at your crew. Move the cursor over any character on the party formation screen and press triangle again to bring up your choices for making changes. You'll see you can change equipment or abilities or change jobs. Be careful when you change to a new job at first because you won't have many skills learned for that new job. Make sure you choose a good secondary ability in order for that character to be useful in the meantime.
Secondary abilities are very important. Under the Ability option of the character changes screen you can set your secondary job ability, your defensive ability, support ability, and movement ability. Picking a good secondary ability means your new Knight character will be able to throw stones or accumulate (Squire abilities) or use potions and phoenix downs (Chem. abilities). I should warn you, if you use the chemist abilities, you will not be able to throw the items farther than the square right next to you unless you learned the chemist ability 'Throw Item'.