There is no such thing as a best opening. At any level.
What is the best openning?
Sort:
Gambits explore the question of giving up something tangible (usually a pawn, generally White offers it but not always) versus the intangible lead in development White gets in return. Games can be open, semi-open or closed. Center control can be via pawns or Bishops. You'd have to decide based on what style of play you feel comfortable and competent with.
What is the best openning for 2000-2300?