Abaddon is best played as a supportive tank. Therefore he should have Heart to take more hits, and Radiance to help draw fire. A Diffusal in early to mid game helps a lot in ganking, and can be upgraded to Manta later. Manta is a great item on him, allowing him and his images to mark different targets with Frostmourne, and they get the increased AS too. BoT is standard for better chasing.
If the game lasts any longer, I suggest Buriza for more damage or Linken’s for more survivability.