League of Legends (LoL) Question: Build paths on Ekko, is it really alright?

I play a lot of Ekko, more like I main him, I 90% of the time go Rod of Ages first into sorc boots into Rylai. Then depending on how the team comp and items are I will either go for rabadons or zhonyas into void staff or Zhonyas into Rabadon then void staff. Or if needed I will go subsitute the void staff for a Abyssal Cepter (not sure if I spelt that right) for ap and mr. I was wondering if my build path is completely wrong. People say you should build for burst but when it comes down to it, would building health + ap be more benifical for your ult to catch up and cause more damage. When at full build I nearly have 800 ap. Even before hand I think the RoA and Rylai help a lot more than Necronamacon does.