Setup SPF, DKIM and DMARC. If everything's passing you shouldn't have any issue delivering to Gmail unless your IP is on a blacklist somewhere.
Check that here: http://whatismyipaddress.com/blacklist-check
Check that here: http://whatismyipaddress.com/blacklist-check
However, deliverability has become really difficult. It seems during the ten years since I last ran my own e-mail, it has become an oligopoly. I have SPF, DKIM, DMARC and reverse DNS, my IP is not on any blacklists, and still my e-mail ends up spam listed in both Gmail and Hotmail. It seems to be getting a worse treatment by Hotmail but it's hard to say due to the small volume.
It is getting better but slowly, it seems.
I had some issues with Gmail but adding rDNS IPv6 and enlisting into DMARC fixed it.
I sent about 125k per week, 80% gmail, no serious issues (I would known cause users pay for email's content).
mxtoolbox.com