Building My Own Push List + System

I am thinking about building my own push list and system for hitting them with messages and ads. I've generated like 50,000 subscribers for a few different companies over the past month and it seems like it might be a good opportunity to build something of my own.

I know some of you are already doing this so I thought it was worth starting another discussion

OneSigal seems like a good option to do my initial test on since they'll support your first 30,000 subscribers for free. Anyone else have a better solution? I assume implementation will