I need to pour small stair entry into my basement, about 4 steps and it is narrow, with a brick retention wall on both sides. I was going to first evenly grade and pack the dirt, then put gravel, then pour concrete (forming and rebar aside). Does that seem like a good layering strategy? When I was pouring concrete indoors in my basement, I also used foam panel insulation and vapor barrier under wire mesh rebar and above gravel but those two parts I don't consider necessary because it is outdoors.
If you are building the stairs tight to the house, you need to go to the frost line with your concrete foundation. Run cinder block to just below the grade level, then go to the brick finish. If the stairs are small enough, just pour the concrete just below the grade and start your brick right from there. Many stairs have been built with a dirt infill then 4" of gravel over that, all on top of the footing slab. I feel that is an error in doing it that way since the dirt can take on moisture and freeze in winter. All gravel under the pour for the stairs, on top of the footing slab will keep heaving and cracking from freezing temps.
The concrete footing, depending on the area could be fairly deep in the ground. Typical concrete footings need not be no more than 8" thick. In my home state of Maryland, the frost line is 30". Brick is an expensive material--to save money, 2 courses of 8" block and 1 course of 4" solid block laid flat can be added on top of the footing to the grade line, then use brick from the grade up, for a nice looking finish.
The plastic under the concrete also help slow the rate the water escapes the concrete, in essence keeping the concrete better hydrated, making it stronger. Foam panels will do nothing for it.