My man, let me break this down in a less aggressive way for you.
Testosterone is recommended for first cycles because BY AND LARGE, it is the most well tolerated anabolic substance for the majority of the population. Its side effect profile and impact on hormones is both well studied and well known.
Different anabolic substances have different impacts on hormonal and metabolic health. The reason that everyone is saying testosterone for a first cycle is because it's very easy to manage its impacts on the body.
Furthermore, many anabolic compounds require a test base for the majority of users. Deca and primo are great examples. Deca is suppressive of endogenous testosterone production, and itself does not aromatize to e2. For most users, this means using deca alone without a testosterone base will crash your test and crash your e2, which is a disastrous state to be in. Similarly, primo will supress endogenous production and actively lower your e2, resulting in crashed e2 as well.
The more compounds you add, the more you need to manage their health impacts. And if you don't know how your body responds to an individual compound, then you won't know how to fix issues that crop up during a cycle.
Your reaction to test c was most likely a result of uncontrolled e2. Too much e2 can cause wild mood swings. Running a large dose of test without having a way to control your e2 will result in _exactly_ what you described.
Maybe we're all wrong, and the science is all wrong, and your body just can't handle exogenous testosterone. But that is an extreme exception to the rule, and the advice you're trying to give your friend is more likely to cause damage to his health and well-being.