To upgrade quickly, it's definitely the fastest to put level 4 dishes, because how many servings your restaurant sells per hour is certain. Then you can have four experiences for each level 4 dish. All-sales dishes can maintain high efficiency.

But you should have enough time, because only one dish sells quickly, and you should add it every few minutes. So the fastest upgrade must be the most time.

After several hours without serving, three dishes could not help serving. After all, it is more cost-effective to sell 3-level dishes than nothing.