To buy shard armor you either have to visit the NPCs in Moors Of Ykesha or you should find a crafter who has the adequate recipes to craft the pieces you need. Tradeskillers can commission craft your pieces for 1 shard less for T1 armors and 2 shards less for T2.
In order to obtain void shards you have to do quests and/or finish some instances that have been introduced by TSO. There are 3 zones in CL, 3 in EF, 2 in Lava and 5 in Moors. Also void shards drop in raid versions of the sama zones. Just visit  for more info.