Go easy on the salt, canned tomatoes already have salt inside. You can use fresh tomatoes for your sauce. The tomatoes should be very ripe. Blanche the tomatoes in some boiling water and remove the skin. Puree in a blender or food processor.
Some people like to remove the seeds of the tomato by straining.
I just use the whole tomato. I usually don't use oregano in my sauce. If you added to much spice, don't worry. Just dilute your sauce with another can or two of tomatoes. Fine Cooking Fine Cooking gives you the tools you need to become a great cook.