Relative Half-Cell Potentials?

Best thing to do is to look up Activity Series and the standard reduction potentials of the reducting/oxidizing agents you listed above and work from there. The lower the value the more easy oxidized they are. sodium for instance easily becomes Na+ by giving up its valence electron and going from oxidation state 0 to +1. It has a value of like ~2.00 or something. Gold on the other hand is the least likely to be reduced, with a value of +2.00 or something. Don't use Ecell formula, because from what i understood youre not trying to find the voltage of a cell.