How about a 100% reduction in departments that have no Constitutional mandate?
Many agencies are dups and can be combined and some eliminated. Get rid of Child Care for workers, let them find their own baby sitters or day cares. Fitness centers, hair cuts for Senators, lots of small places you can cut, that make a big impact when rolled into one ball of wax.
Why have 6 staffers when 4 will do? Why do the staffers need aides, why does congress need aids, interns and lobbyist? Make they do their own work. Work them 5 days a week not 3 like they do now. Gut some fed holidays.