pacanis, i could go on for an hour about red gravy. maybe longer.
it was the first (and probably only) thing that i've really tried to understand and perfect in my cooking lifetime.
there are a huge range of both flavors and textures in the sauce.
from tart - raw tomato flavor; to deeper, sweeter sauces. there's cleaner veggie flavors; to meaty, spicy, or even fishy tasting.
in textures, there's very smooth, to very chunky. thin to thick. even ones with fresh tomatoes added at the very end.
i like the idea of small batches for testing, and agree with all of what andy and gg have said.
i would start with making a thin, smooth, tart sauce. just a heated can or two of chopped and/or pureed tomatoes.
then add herbs (oregano, basil, parsley) a little at a time, and start tasting.
next, add some toasted garlic and onion to see how it sweetens and changes the sauce. if you aren't getting the sweetness you like, add a tsp or 2 of sugar. to thicken it, add a tbsp or so of tomato paste.
that's the very basic sauce. you can change the texture towards more chunky by using hand-crushed whole tomatoes, and letting them cook in. or any combination of smooth and let processed tomatoes in between.
you can decide along the way if you want extra levels of flavor by adding such things as a little anchovy paste (disintegrated in the olive oil while the garlic was browning is best, imo); alcohol, such as wine or vodka; or a tsp of hot red pepper flakes and/or capers to spice it up a bit.
also, veggies like bell peppers, mushrooms, carrots, and zucchini will bring more flavor, and texture. you'll need to experiment on when to add them: if you want them to cook into the sauce or if you want them more fresh. not all of your red sauces will require these.
next, there's the addition of browned meats. start by making beef meatballs. it'll change and deepen the flavor considerably.
then there's browned sausage. another huge change in the sauce's flavor. they're my favourite thing to add, besides browned pork rib ends.
ok, gotta stop now, work calls. not sure if this makes sense yet. i'll edit and add more later.