The effect of baking soda on water electrolysis
Definitely do not used stripped copper wire, unless you fancy a nice blue solution and electrodes that need constant replacement. You see, copper oxidizes quite readily, so you will end up with lots of $\ce{CuO}$, and a loss in the yield of $\ce{H2}$ and $\ce{O2}$. The best things would be noble metals like platinum, but stainless steel should do fine for your purposes/likely budget.