To put Viliam's (very good) suggestion in more concise, specific terms: try casting the network of ideas in your head into a directed, acyclic graph of dependencies. That might make it easier to systematically begin with the ideas that lack dependencies, and proceed from those.

(There's a good chance you've already reformulated, in your own mind, what Viliam wrote into these terms. But I thought it worth mentioning in case you haven't, though I run the risk of patronizing you!)