Your question is a bit too vague, as there are too many sauce variations to choose from. There are the meat sauces known as Bolognese, there are ragus, Alfredo, oil and herb dressings, cream sauces, veloute's, brown butter sauces, etc.
If you are looking for something resembling Prego, or Ragu brand pasta sauce, start with tomato sauce and tomato paste. The herbs and spices can then include any or all of the following;
Oregano
Sweet Basil
Rosemary
Thyme
Marjoram
Fennel
Black Pepper (optional)
Cayenne Pepper (optional)
Salt
Garlic
Onion
a little bit of sugar or brown sugar (optional)
Sage (optional)
The primary flavors that most American Spagheti Sauces contain are Oregano, Basil, Rosemary, Thyme, Garlic, and Onion. after that, you can add everything from cottage cheese, to nutmeg, depending on the flavor profil you are trying to get. I recomend starting with the 5 flavors first mentioned in this paragraph. expand from there. And remember the two cardinal rules of sauces:
1. add a little herb or spice at a time, let cook for 15 mintues or so, then taste. Correct from there. You can always add more, but once it's in the sauce, you can't remove it. Do not overpower with too much herbs or spices.
2. Patience is required. Cook over low heat to avoid scorching the natural sugars in the sauce, and to allow the flavors time to permeate the sauce.
The herbs and spices I provided are my choices for the style of tomato sauce I prefer. I also use chunky tomato sauce with lots of veggie chunks comprized of green and sweet peppers, onions, and musghrooms. I love big chunks of ground beef in my sauce as well. You might like yours different. I can't tell you how to make the best sauce. Only you can create your favorit, based on what you like.
Seeeeeeya; Goodweed of the North