So much of ingredients/products for your hair depends on your hair properties (individual hair diameter, density of hair on your head, porosity, and elasticity) that determining these is really important. There is a guide here look at the light blue band at the top of the page and read the things under "Hair Types". And another at Live Curly Live Free - Home
where you can order a hair analysis. I copped out and ordered the analysis. Once you know your properties, you can look at the information in people's signatures and find what works for others with your properties.
A conditioner for co-washing can have cleansing properties. One that is popular and that I use is Suave Naturals. They have EDTA in them and I like that because I have hard water and EDTA is a chelating agent. Depending on your hair properties, you might want your leave-in to be lighter or heavier than your co-wash. Some are able to use the same conditioner for both.
How your hair will react to a protein treatment can also depend on your hair properties, so it is best to figure that out before you try using one.
It can be overwhelming when you start, but with a little time, reading, learning, it does get easier.