Well, I started with (vb) Rhinoscript in 2009 (Python for Rhino did not yet exist) and was reasonably proficient after perhaps 6 months. I did take a 3 day class in Rhinoscript offered at McNeel Barcelona at the time taught by Luis Fraguada, and also worked through the Rhinoscript 101 primer by David Rutten.
Switching to Python gradually starting in 2011, I picked up a book on basic Python programming (there are tons) and started with rhinoscriptsyntax, which is basically the vb Rhinoscript methods adapted to Python. From there I just kept going, delving more into into RhinoCommon as time went on.
There is that initial “hump” to get over where everything looks completely foreign and abstract and you think you will never understand. However, once you get the hang of a few basic programming/scripting principles and a bit accustomed to the level of abstraction, it gets a lot easier. Everyone’s experience will be different, some people pick this stuff up really fast, others just never really get into it.