Basically there are a few considerations to make when planning a custom food. They are: HP, stamina, food, and weight. Making a good recipe requires a delicate balance of all these. Its also important to note that this is a great way to store surplus food that would otherwise rot. Custom consumables have an extremely long shelf life when refrigerated compared to normal food.
Only eight stacks of ingredients can be in a single recipe.
Drugs and pre-made Dishes can not be used in a recipe.
If eggs are used in the recipe, the recipe is specific to that type of egg.
For a food filler, it's typically made of RAW meat. The best one I have is 10 raw meat for 101 food. Cooked meat technically gives more food, but I like the extra heal from raw
Element dust is a FANTASTIC ingredient. High stats evenly distributed with good weight
For healing recipes, try to use 2-4 bee honey and the rest of your 8 recipe slots some prime meat.
Mushrooms in general just make better recipes; primarily because they have more balanced stats. The downside is they lack real sustenance as food to fill your hunger. However, food is the easiest stat to fill almost without trying.
Stimberries and Auric mushrooms would normally decrease your water; but in a food recipe, they do not lower your water stat. It still does reduce the water given by a drink though when included in the drink's recipe.
DO NOT USE EGGS - THEY ARE MASSIVELY HEAVY! You're better off turning the eggs into kibble and using that in a recipe for the insane stamina regen. KIBBLE GIVES A TON OF STAMINA
Crops/veggies are best used in drinks. 2-4 on a good crafter will fill your water to 100
Please pay attention to weight. You would not believe how much extra room you can make just by getting rid of your egg recipes and doing meat or mushrooms instead.
KEEP IT SIMPLE. I tried making recipes with 4 or 5 different ingredients but it just leads to a big hassle that totally isn't worth it.
Also, note that recipes don't really become "worth it" until about 500% - 550% CS. That is the turning point when you start to reap benefits instead of taking losses.
To find out what ingredients have what effect, check out this guide: Ingredient Effects