I think the key is really all in the brand and type of tomato you use more than anything else. Go out and buy evey type of quality tomato you can find and open them all at once. Try them right from the can, and you will find that they vary widely. After you have found your favorite tomato (I prefer to start with whole tomatoes), the key is getting the right moisture content for your oven/style. You may have to drain a lot of moisture out of them. Jeff Varasano swears by his technique of draining out more moisture than you need to and replacing the liquid with spring water.
Once you have great tomatoes and the right moisture content there is no need to do much more, but you can always try adding things like oil,basil,onions,garlic,salt,pepper,red pepper flakes,oregano, etc. Try to do this in moderation. This can even be done (with the herbs) right on top of the sauce as you are putting together your pie. The herbs taste different on top of the cheese, and that might be fun to experiment with. Sometimes I saute onions and garlic in some oil and then combine that with uncooked sauce. Sometimes I just put fresh garlic uncooked in the sauce. Sometimes I do absolutely nothing to the tomatoes but get them to the right consistency. Trial and error will get you to where you want to be, but the ultimate key is to use the right tomatoes.
Lately I have been finding really good tomatoes for cheap in the grocery store for some reason. I have been slowly roasting them in the oven do get the moisture out and concentrate the flavor before pureeing them into a special occasion type of sauce. PFT uses fresh tomatoes and does not even concentrate them in any way and I am sure his sauce is amazing.
California tomatoes taste very different than Italian ones, and you should try both to see what you prefer.