Gustavo follows these people on Refind.

Moz
Software and resources to help you take full advantage of the power of SEO, whether you want to drive customers to your website or to your front door.
Brian Dean
I teach people how to get higher rankings in Google (and YouTube).
Neil Patel
Entrepreneur, investor & influencer. Columnist for Forbes, Inc, Entrepreneur, Huffington Post & more. Founded @CrazyEgg with @hnshah.
HubSpot
HubSpot offers a full stack of products for marketing, sales and CRM: powerful alone, and better when used together. Use @HubSpotSupport for Twitter support.
HubSpot Academy
We aim to educate and inspire people so that we, together, transform the way the world does business.
SaaStr
A curiously popular blog turned global SaaS community focused on web services people pay for. @saastrannual in Feb @saastreuropa in June + work @cosellingspace