Understanding GaryVee and Julius Dein's Audience
The audience that GaryVee and Julius Dein share on Facebook and Instagram is… a mass-audience of 15M-20M active users per month. They’re mostly men (75%) between 18 and 34. Most of them are single and went to college. The biggest chunk of this audience lives in the US (20%).
Here’s a quick overview to give you a better sense:

Activity
This audience is significantly more active across the board than anyone else. On average, a GaryVee/Julius Dein fan wrote 14 comments, liked 30 posts and clicked 26 ads in the past month.

Who or what is relevant to this audience?
The brands that are highly relevant to this audience are very much personality-driven. As you can see here in this top 25 list, it’s all about people and their success/beauty/fun lifestyle:

A few things I noticed: Not many of the brands this audience also very much likes run ads. GaryVee, Jake Paul and Curtis Lepore are the only ones running full-blown campaigns. From the look of these ads, they’re running mostly on Instagram.
GaryVee’s most interesting campaign is all about teaching entrepreneurship to this younger audience. I think he’s honing in to this age-group very well with attention-grabbing along the lines of “your mom is holding you back.”

What to do with this information?
My first instinct here is that this audience is FAR too large to effectively address. Go much, much smaller and more specific.
This is more of a “generation” of mostly men than a type of person (or persona) that you can serve – I would highly recommend narrowing your focus down to a smaller sub-niche (250K or smaller) whose pains you can understand deeply and serve better.