In SWTOR you have light/dark points at 1000 point you have tier 1, where can I buy it or just it is a requirement? is it PVE set? how can I buy the pvp set?
The word “tier” has nothing to do with armor, it's just another word for a rank.
In WoW, it means how good your armor set is. In TOR it's used to describe how much along the light or dark side you are. Some armor has restriction for for example “Tier I Dark Side”, but there is no single Tier I armor or armor set.
In SWTOR, the Light/Dark system can provide armor or weapons ( it's a requirement for some pieces ), but not in the way you are thinking. The Light/Dark is the mechanical guide to how closely your character follows to the ideals of the Light or Dark side of the force.
To buy specific Light or Dark side pieces, you should find the Galactic Trade Market area on your 'Fleet' area. There should be a Light Side vendor at one end and a Dark Side vendor at the other ( on the outside of the curve ).
However, I would advise against LS/DS gear, because other than the relics, they're all pretty crappy and would be replaced by better gear fairly quickly.