Create a new common event. Leave the trigger to None. In the event commands, add a Control Variables. Create a new variable, choose Add for the operation, and 1 for the constant value to add.
Then add a Conditional Branch that says if the variable you just created is equal to 3. Inside the conditional branch, add the state you want to add.
On your Item, add a new Effect. On the Other tab, choose Common event and select the common event you just created.
Now each time you consume that item, it will add 1 to the variable. After you consume 3 of them, the state will be added.
If you want the count to reset, so consuming 3 more of the item will add the state again, go back into the commands inside the conditional branch, and add another Control Variables. Select the same variable, and this time use the Set operation, and make the value 0.