This takes 5 minutes if you do my method.
Start tutorial level (skip tutorial) go up the stairs then go right up another stair. Here is the salesman where you purchase emeralds.
Pick up the 60 pages in the item box now save your game.
You can trade for 2 emeralds then exit to main menu (disable autosave-confirm, exit without saving confirm) do this every time.
Keep loading your save and get 30 emeralds quickly.