I think there is no final answer to your question, it depends a lot on what kind of future the job can give you and how high your chances are to find another job like that in case you loose it. But I would always say: It is better to have a "Ausbildung" first before you start working.
The reason is, that a.) you get more money (most of the time) because you can show that you have a qualification.
b.) your are more safe in your future because once you might loose your first job, the next opportunity will maybe require an "Ausbildung" and they will pay you less or not even hire you without that.
The negative part about starting an ausbildung first is, that you will not earn a lot of money in your 3 years of "Ausbildung", and you might have to get financial support in this three years. But all in all, in my oppinion it is worth it!
All the best