Dearest CoCo. I am conflicted at the moment, and so have not read all previous posts. Forgive any repetition.
As for Mac and Cheese, I think the key is adding cheese to the top and baking, everything else is just gravy. Figuratively of course.
As for oil. Olive oil must NOT get too hot. I've read many a comment that says use it after cooking is done for flavor and health. Ohh California has Olive Oil, and I think it's wonderful. Try Sciabica's. You might find them at your local farmers market, and get to sample the varieties. I agree with Outlaw on Canola Oil. It also changes when heated, and becomes not the healthy oil it has been touted. Grape seed Oil is wonderful stuff. Healthy, takes high heat, is flavorless, and rather "thin". Your local Trader Joe's will probably have the best price, it can be expensive.
As for pricey shopping, I say there are some things you want to spend on, and others that just as good cheap. I prefer fresh veggies in season, but my understanding is that frozen is equally healthful, sometimes more so. Travel time, field to store, etc. Currently I have a lovely fresh herb collection in pots. I am hoping for a full garden next year.
IMHO, onions, garlic, spices, herbs, and love can transform any ingredients into a feast.