You might find it fitting to start with Oppose Book Worship, which deals with just the problem of overly-dogmatic comrades that only ever read theory. You must read theory and test it via practice, each informs the other.

I'll also shamlessly plug my own Marxist-Leninist reading list again as it's designed for people to go from knowing no theory to having a solid grasp of the fundamentals of Marxism-Leninism, as well as its historical context.