How much hydrochloric acid (maximum) should I use to do electrolysis of water, and how much amount of voltage should I use to get the maximum of hydrogen and oxygen?
You will not get oxygen if you use HCl, you will get Chlorine gas instead.
You could use sulfuric acid (like your title said before someone edited it) or NaOH as an electrolyte.
0.5 M would be a reasonable concentration.
You need to see the concentration of acid. If it is a concentrated acid, you will get chlorine gas. But if you use diluted acid, you will get oxygen gas.