I only generally buy dried spices and herbs, and canned fruit/vegetables/lentils. I stay away from packet mixes and jarred sauces as I prefer the taste and satisfaction of home cooked. I also like to know what's in my food.
I personally think that home cooked doesn't really take that much longer than using a packet or jar if you were to know the recipe by heart. Once I have cooked a recipe once I pretty much remember the recipe from then on in. Also I will make pasta sauces etc and freeze them for those nights where I don't really feel up to cooking a whole meal from scratch.