Electric bills are brutal, do I start with windows or attic insulation?

Our 1970s colonial near Hartford is drafty and the bills prove it. I have maybe $8,000 to spend this year and everyone I talk to sells whatever they happen to install. Window people say windows, insulation people say attic. The house has original single pane windows with storms, and the attic has maybe four inches of old fiberglass. Where does the money actually go first?