Stargate Universe/Atlantica clarification?

Start with Stargate SG-1. If you like, start with the movie Stargate, which starred James Spader and Kurt Russell, then watch the series Stargate SG-1. It lasted for 10 seasons. Stargate Atlantis was a spin-off that started around season 7. Stargate Universe is the final, and worst, entry in the franchise and well worth skipping. You can watch Ark of Truth and Continuum after the end of SG-1.