Knowledge you will need
° Basic Maths (Algebra, geometry, trigonometry, basic probabilities).
You don't need to be a rocket scientist, but maths are part of the tools to use in C2 and development in general. Having high school notions is more than enough to solve any problem you might have to face.
Also a lot of maths functions are already part of the system expressions
Being realist about the time/possibility of implementing features/making a game.
If this is your first game you have no reference, maybe no idea how much time it will take you. That's why all along this tutorial I insist on the fact of getting familiar with all what C2 provides, with discovering exploring a lot (IDE, manual, tutorials, forums, experimentation). This will help you this famous estimation.
And any program/piece of stuff you do, you can save and keep in your own tech-library (a dropbox folder in which you save small capx of specific features/mechanism to which you can go back and share in need).
Don't launch yourself in the cloning of a zelda if your alone and beginner. Strike for simpler. A snake game, a memory game, a simon says game, an arkanoid clone...
Start small, increment onward. You will feel rewarded at each step and gain more experience this way.
The video is talking about the game making industry (big companies, numerous employees, etc...)
In the hobbyist point of view, your reffering value is time. How much time does it take you to implement the game ? To release it ? To consider it complete ?
For an independent it is a value time/money. You're spending such amount of time on making a game expecting a X return for the time spent, allowing you to make a living and investing in your next game.
Or you may aim at niche markets. There is also the time/money ratio to take into consideration but you are also more relying dependant on the community you're making the game for.
° Basic User Interface Design
As said in the video, at some point, even if you're not a graphist/artist, you have to build a usable UI.
This is more about designing than actual coding, but even a programmer should have basic knowledge on this subject.
As a game maker it is primordial that you tackle the concept of User Interface Design. The experience of your player depends on it.
"See it from the user perspective, it's primordial"
° Low level language
In the case of C2, you can almost spare this part. C2 does the heavy lifting for you so you can focus on design.
It is heavily interconnected.
° Understand how computers work
Knowing what a computer is made of and how it works is a basic knowledge to any game video designer.
Know the support on which your game will run. (PC, Mac, Windows, Linux, mobile phone, tablet, iOS, android, etc...)
The manual entry gives a good overview of what you need to know and take into account for your C2 games, as well as the blog article about C2's architecture.
° Make your game
Every day, even if it is only 10 minutes. Get it done whenever possible.
Getting some portions of the game made helps designing it, a good design help to program it in C2 quickly and efficiently.
"By forging you become a forger", literally translated French proverb