I absolutely agree. Obviously, making money is something important during App development. However, we are very limited to how we can utilise advertisements. Not having access to rewarded video advertisements is a big no. You may argue that you can do that in Tier 2 But AppGameKit promises easy game development, but learning C++ is no easy task and not being able to do this within tier 1 is a large problem.
Now for the above replies, To sell your apps you would need a Merchant account, (which from my experience) you need a legal business in your country which not everybody can do. Please let me know if there is a way of selling apps as an individual without getting involved with the government.
Also, since your making your first app, let me explain what you can expect from advertisements, also from my experience. From 2 apps, (~1800 downloads) 8000 advertisements displayed and 239 advertisement clicks, 130 Euro. Might not sound like a crazy account, but make a REALLY successful app, and this will add up. Say you made an app with 50k downloads, which is very possible if you make a decent enough game and right advertisement, using our statistics, that would be 3500 euro. Now, this is without any rewarded video ads, and without any in-app-purchases. Damn. Not bad at all? Really makes you think about the games with millions of downloads.
As for admob, you might know already, but if not, In order to get paid you must reach a minimal threshold of 70 Euro. Estimated earnings are also not the same as finalised earnings, which in my case i seen a 7% drop.
Goodluck with your first game!