How could I be ArcGIS developer ?

[JokerEsri]

Hello , 

How to be ArcGIS developer ? 
I have experience in Fme and Python 

But how could i start to be ArcGIS developer ?

which courses should I watch ?what should I do ?

[jcarlson]

I'd suggest diving into the Developers site. You can find loads of documentation, examples, and tutorials, and you can start working with things like the JS and Python APIs right away. Courses are all well and good, but I'd say you're better off to just get your hands dirty and start building stuff.