TDC's Trading Sequence Walkthrough for The Wind Waker is incomplete, so here is a complete one:
1. Talk to Zunari on Windfall to get the Town Flower.
2. Trade Town Flower and 20 Rupees on Greatfish for the Sea Flower.
3. Trade Sea Flower and 25 Rupees on Greatfish for the Exotic Flower.
4. Trade the Exotic Flower and 55 Rupees on Mother & Child for the Pinwheel.
5. Trade the Pinwheel and 40 Rupees on Bomb Island for the Sickle Moon Flag.
6. Trade the Sickle Moon Flag and 85 Rupees on Mother & Child for the Big Catch Flag.
7. Trade the Big Catch Flag and 60 Rupees on Bomb Island for the Fountain Idol.
8. Trade the Fountain Idol and 60 Rupees on Greatfish for the Skull Tower Idol.
9. Trade the Skull Tower Idol and 35 Rupees on Mother & Child for the Big Sale Flag.
10. Trade the Big Sale Flag and 75 Rupees on Bomb Island for the Hero's Flag.
11. Trade the Hero's Flag and 100 Rupees on Greatfish for the Postman Idol.
12. Trade the Postman Idol and 200 Rupees on Mother & Child for the Shop Guru Idol.
13. Trade the Shop Guru Idol on Greatfish for a Piece of Heart.
14. Talk to Zunari on Windfall for the Magic Armor. Technically speaking, you can do this when he has at least four items in his shop.
15. You need to pay a total of 755 Rupees to complete the Trade Sequence.
If you need to get Rupees fast to complete the Trade Sequence, I recommend using the pots on Windfall, going to one of the caves with a Triforce Map and breaking the pots there, or playing the mail game on Dragon Roost.