We have the gate that Candaceb posted and used 2 of these Kidco K12 gate install kits so we didn't have to drill into the banisters. (we ordered from amazon- you do need a drill to drill the hardware into the plastic thing that goes around the banister.Even though it says no drill.) I think that gate could work for you at your front stairs top (with 2 kits) and maybe the front stairs bottom with one kit and drill into the wall for the other side.
You could also use it on the back stairs at the bottom. The complicated part looks to be your back stairs top with the window. Depending on how low the window goes you might have issues figuring out how to secure a gate on that side.
Start looking at CL or local consignment stores or FB pages (we have a local FB "garage sale" page) and get gates used if at all possible. I got a gate on CL and one my friend "lent" me one but without hardware. Kidco was great helping me figure out what I needed and got it to me really quickly.
jeri
DS 6/10/06
DS2 9/1/10