I don't know if i am to late but i answer the question anyway
To make a good electrolysis/drycell you will need an anode and katode that cant corrode. Aluminium, copper and normal steel wont work at all.
I suggest that you buy stainles steel, that will work well, and of course both the anode and catode is made by the same material.
There is many choices of an electrolyte, it depends in what way you is going to use it. I would say that your best options is baking powder, Potassium hydroxide (sometimes hard to get your hands on, is verry corrosive) and Sodium hydroxide (often used as a drain cleaner allso verry corrosive).
If you are going to use your cell in short periods of time (not in a car) and you are pretty new to this, i recomend baking powder becaus it is not dangerous to work with at all. But eventually it will discolor your water.
The second best choice is NaOh it produces cleaner hho and will keep your electrodes clean but remember that it is dangerous to work with. Handle it with care.
KOH is the best electrolyte of the ones i have said. It is a stronger electrolyte it will do the same thing as the NaOh but it will work better. And allso remember that this one to is verry caustic, you dont want to get it in your eyes
I hope i helped you with something feel fre to ask more questions!
Sry for my bad english
Edit* I have been looking for a verry long time for an effective electrolyte that is not caustic or corrisive but it seems like that is allmost impossible im sure you can find it somewere but i think you will have to search for a while then