In the state of South Carolina, how much am I allowed to contribute to my local congressman’s election?
The US Congress is a Federal, not local office. So per the Supreme Court’s stupid decision in McCutcheon v. Federal Election Commission, there is no limit on contributions to your US Congressional Senator or Representative.
If you meant your local SC Legislator, you can contribute $3,500 for the Primary election and another $3,500 for the General election ($7,000 total).