There are five simple (as in simple to understand and express, not to implement) amendments to our Constitution that need to be made that I think would cure all our institutional ills:
1) Term Limits: Not just at the federal level but for all elected offices in the country. My thought is that 12 years for legislative offices and 8 for executive. This would not prevent the existence of career politicians but it would make them have to change jobs more often.
2) Abolish gerrymandering: This could be simply done by requiring that all federal districts be made up of whole counties with the exception of those that are smaller than the single county in which they reside. Those geographically smaller urban districts would be required to be made comprised of whole municipal subsections.
3) Statute of limitations for statutes: All laws will expire 20 years from passage unless re-passed. Only the US Constitution and State Constitutions would be permanent unless constitutionally altered.
4) Statute length limitations: No single bill longer in word length than the US Constitution may be passed.
5) National Referendum: All federal laws and rulings of the Supreme Court may be overridden by a national referendum held every four years. I don't know whether it would be best to have it on a presidential year, a midterm election years, or an odd year election to completely separate it from federal politics.