I cannot +1 Peter V because of my poor reputation, but he is right: in Italian cooking you don't go for mix, what you look for is a balance between a few ingredients, normally one from different kind of foods: one cereal, one vegetable, one spice for example.
The main spice (or fresh herb) is parsley: it is so common that it is used in figurative language as well
, think about a celebrity you see everywhere, just like parsley.
Fresh basil is a must for spaghetti sauce and freshness, as Peter V said, is the only option.
I never heard about red pepper in Italian cooking; I bought mine during a travel in Asia and use it for Asian food.
Black pepper is for sauces and meat, white pepper for fish, normally.
Oregano, thyme, marjoram, are common, and they normally don't mix.
Oregano is widely used on the top of some pizzas, especially when they have got anchovies, capers and/or olives on top.
Pizza margherita requires fresh basil.
Rosemary, bay leaf and sage are used commonly with meat or beans/lentils: in this case you often prepare a bouquet tying together some small branches from these three herbs with a cooking lace and let the bouquet rest in your preparation for some time.
You should probably add fennel seeds to the most-common-Italian-spices list.
cooking.stackexchange.com/users/17664/Sergiof4
Having taken a look around some recipe sites and taken the intersection of what most of them consider the "core" spices (and leaving out the ones that showed up on too many 'variations' lists), it looks like the canonical ones are: basil marjoram oregano rosemary thyme
cooking.stackexchange.com/users/134/Adrian Petrescu
I applaud your spice growing!
But, I would recommend you not mix your spices into a homemade Italian seasoning mix, for a few reasons.
First, some of the core mix are better dry, like Oregano --
Oregano needs to dry out to attain full flavor.
Others, like Basil absolutely suck dried out, and taste way, way better fresh.
Most spices taste better fresh.
Second, most legit Italian food doesn't use a big mix-o-spices.
Classic Italian spaghetti sauce is actually just: milled tomatoes, olive oil, red pepper, salt.
And it's unbelievably good, and indisputably 'Italian' tasting.
If you're going crazy, you can throw some torn up basil leaves into the pasta.
Maybe you get where I'm going with this -- usually Italians cook with fresh spices, trying to bring out the individual flavors.
Having your own herb garden will get you there fast, so don't worry about making the mix.
(But do grow all those spices listed here, you'll use them!)
cooking.stackexchange.com/users/982/Peter V
I think generally it is basil, marjoram, oregano & sage usually in the ratio 2:2:2:1 although it can differ and sometimes contains rosemary too.
cooking.stackexchange.com/users/210/Sam Holder
I would throw in Bay Leaf as well, along with dried red chilies.
I think the standards are Basil, Thyme, Oregano and Marjoram...
Rosemary is not always considered Italian.
cooking.stackexchange.com/users/215/nicorellius
There is rosemary, thyme and oregano in the Italian seasoning.
cooking.stackexchange.com/users/23141/isabella
basil, oregano, parsley, rosemary,thyme, marjoram,sage, sea salt, black pepper.
cooking.stackexchange.com/users/25540/user25540
We use marjoram, oregano, basil, thyme and bay leaf in Italian.
If you can't have fresh then perhaps roast the dry seasonings together in a hot cast iron skillet, dry.
cooking.stackexchange.com/users/29229/John
The main three Seasoning are oregano, parsley, and basil.
Other can be used rosemary, thyme, marjoram, sage, sea salt, black pepper, truffle salt.
cooking.stackexchange.com/users/44705/Alma Dolce
I'm beginning to grow my own herbs and would like to put together something similar to the "Italian Seasoning" found in the grocery store spice section.  (It's an easy way to add more flavor to pasta sauce.)  Is there a commonly accepted list of ingredients and proportions, or does it vary between the spice companies?
What herbs and spices are in "Italian Seasoning"?
cooking.stackexchange.com
<spices><herbs>
cooking.stackexchange.com/questions/1485
cooking.stackexchange.com/users/628/Rob Walsh
The main seasonings are oregano, parsley and basil, followed by thyme, rosemary, marjoram, bay leaf and sage. Different Italian dishes will require different ingredients and fresh basil is a must for spaghetti sauce. A good mix would be parsley, basil, marjoram, oregano, sage and thyme.
A good mix would be parsley, basil, marjoram, oregano, sage and thyme.