Sustainable cooking is a function of the amount of time you're willing to commit to cooking and the tools you have at your disposal. A slow cooker, for example, can involve almost zero prep and very little time actively spent cooking (you toss it all in the pot and hit go). A much more involved meal which requires regular attention, on the other hand, might take less total time to cook, but more active time cooking.
I think the best way to provide advice is to get a grasp on a few important factors:
- Price sensitivity/budget
- How much time do you tolerate between starting cooking and eating the food (active cooking + all other time, such as time spent in the oven or slow cooker)?
- How much time do you tolerate where you are in the kitchen actively cooking or preparing ingredients?
- Do you have any food restrictions or preferences?
- How varied do you want your cooking to be? Are you okay with eating the same thing every day or want more variety?