I need 1L of a pH 4 buffer with a total molarity of 1. Propose a buffer system and a recipe to achieve this goal. (acetic acid/acetate would probably be a good choice.) help please!

You know acid + base = 1.0M

You know pH = pKa + log base/acid so plug in pH and pKa and you will obtain the ratio of base/acid.
The two equations solved simultaneously will give you the M (then mols) of the acid and base. See if you can take it from there.