Infinite items
Go to Museville (the second town). Beat one or more pre-determined dungeons, pick a floor with good stuff, get it, then go to town by exiting through the entrance or warp station. When you get back to town go to the same dungeon and the items should still be there. No important items will reappear (upgrade kits, Cyframe parts etc).

Infinite experience
Go to a predetermined dungeon and fight the monsters. If you run out of monsters go up/down a level then come back. If you are hurt exit to town and all your health is recovered and experience points/move points are still with you.