There is no such thing as a good, authentic Italian pasta (not just spaghetti, but pasta) sauce. as there no such thing as a single Italian cuisine.
Italian cuisines are regional, and even within any given region, each community's cuisine will have it's own, basic, differences with the cuisines of neighbouring towns. In addition, each family will have it's own recipe.
The key to Italian cooking is to use the freshest possible ingredients and to not do too much with them.
The best thing that you can do is to check for recipes in the internet, or borrow books on Italian cuisines from your local public library system (you remember the library, don't you?), experiment a bit, and when you find something that you like, keep experimenting to come up with your own favourite variation.
But, since you specifically said spaghetti sauce, you need to remember that long, thing, extruded pastas need smooth sauces, not chunky ones, so unless you're mincing all of those veggies, leave them out.