How can I keep my MacBook, iPad, and Nexus 5 happy?

I'm trying to set up a good system where all of my devices are for the most part almost entirely synced up with each other and all feature the same photos, documents, and other information as the others. Right now I have some cross-platform apps like Todoist, Pocket, Writer Pro/JP Writer, and Chrome filling some of the system-level gaps left between Mac OS/iOS and Android.

The problem is that I don't know which ecosystem I should settle into, or whether I should just forge my own from a group of apps. I use Pages a lot on my MacBook, which syncs up with my iPad, but my Nexus 5 is for the most part left out of the documents area.

And all my photos end up on Google+ through automatic upload, but these photos also don't end up on my MacBook Pro. Which, to me, is a bit of a dilemma. I tried using Picasa, but it was just too confusing (and a bit ugly, sorry).

Can anyone in a similar situation possibly shed some light on how I should set up my devices?