Straighten your derailer hanger. You'll be quite disappointed that a new groupset has the same exact shifting problems if you don't fix that first, and once you fix it, you might not want to waste money on a new groupset. Spend the money on good contact points (saddle, pedals, shoes, handlebar, bar tape) before the drivetrain, then maybe some better tires and/or wheels. These are upgrades where you'll get the most bang for your buck.