Since ingredients are at the top of the list of things you need to have, you'll spend a decent portion of your time in game trying to acquire them. They are collected from different sources. Some are acquired from shops, like Beef. Some you get from "supply stations", like bread and cheese. Some are crafted, like tomato sauce. You can also find a lot of different ingredients by visiting your neighbors.
Visiting your neighbors can help you out a lot when it comes to finding ingredients. Each day you can visit each neighbor, and you receive five energy to use at their restaurant. There are a lot of activities to choose from when looking for ingredients. Pretty much any of the things you can do in your restaurant, you can do at your neighbors. Visit their Mom and Pops shop for a chance to get beef. Harvest their onions, or tomatoes. You can visit each of their stalls, like broccoli, lettuce, or garlic. Also, if your neighbor has any dishes that they are currently serving, you can mouse over each dish to see an ingredient and coins. If you eat of serving of that dish, you have a chance to get that ingredient. So far it appears that its entirely random, but please let me know if you find a pattern to the finding of ingredients at your neighbors place.
There will be a list of the various ingredients in the game here. It will take me a little while to make it a comprehensive list, as I am adding each image for each ingredient as I get the page for each one made. If there is just text, a page has not yet been made for that item.
Thanks for you patience...you can also volunteer to help work on the wiki!
Click the ingredients below to visit their page.