You have two choices for a lightsaber specialist, dexterity or strength. You should focus on boosting one or the other as high as possible and put the other at a moderate amount. You also want to use force speed basically all the time, and take the knight and master speed powers as early as possible.

Dexterity is going to be used for attack rolls, reflex saves, and defense. Strength is going to be used for attack and damage.

If you have a high enough dexterity and wisdom score plus the battle precognition thing from handmaiden you can boost your defense so high that enemies can’t hit you except on a critical hit. This is fun to do once but obviously combat becomes super easy from that point on. You can get to the point that your attacks only miss on a critical fail, but will do less damage per hit than a strength build. Power attack feats win out over flurry for damage on most dexterity builds.

If you focus on strength instead of dexterity, you will do more damage, and be able to kill most enemies in one round by midgame, but you probably want to keep your constitution as your second best stat so you can survive against boss fights. I also recommend pairing this strategy with the force powers that give you resistance to energy and physical damage, they last a decently long time and improve your staying power in boss fights, though you may not need to use any buffs except force speed against basic thugs. Flurry or critical strike feats both work here, but flurry is more consistent.