One, don't mix alcohol. don't mix champagne, beer, vodka, wine, etc. If you're going to drink, you drink one drink. The hangover is caused primarily by congners in the beverage. Congeners are toxins made during fermentation. This includes higher alcohols besides ethanol (propanol, butanol, etc) and other shit.
Vodka- lowest concentration
Gin- Next lowest
Blended scotch- 4x the congener content of gin
Brandy, rum, pure malt scotch- 6x blended scotch
Bourban- 8x blended scotch