Adding Delay on the item is the best way to used it one at a time
example is something like this
Before :
{
Id: 12041
AegisName: "Str_Dish01"
Name: "Fried Grasshopper Legs"
Type: "IT_HEALING"
Buy: 2000
Weight: 60
BuyingStore: true
Script: <"
sc_start SC_FOOD_STR,1200000,1;
percentheal 5,0;
">
},
After :
{
Id: 12041
AegisName: "Str_Dish01"
Name: "Fried Grasshopper Legs"
Type: "IT_HEALING"
Buy: 2000
Delay: 1800000
Weight: 60
BuyingStore: true
Script: <"
sc_start SC_FOOD_STR,1200000,1;
percentheal 5,0;
">
},
Item Delay : 30 minutes