-40 Attack, Strength, Mage, or Ranged.
-A empty space inventory.
Okay first you need to go to a world with not so much people, then go to Varrock palace guards. Kill the guards till you get a full inventory of grapes. Guards dropping grapes are common. Grapes now cost 1.4k, which means a full inventory of grapes are 40k.
Note: Grapes drop in 3's.