Well it depends on your play style really.
I would start with the TEC, their abilities and researches are easy to figure out and use. Their ships are usually fairly cheap and they earn a lot of credits which leaves room for a bigginer player to experiment
Once you've got the basics down, try either one of the other races.
Vasari - expensive ships, intersting techs(like phase gates and phase missles), best resource gathering, needs more micro managing for abilities to work effectively, powerful late game techs, self repairing abilities.
Advent - powerful shields and weaponry, culture dependent, weakest economy, and very expensive technology, powerful late game weaponry, the most micro intensive and ability passive race.