How do you learn to jungle?

Ok...so jungle is the only role I've never played...and I need to play it obviously. Not only does it sound and look enjoyable...but I obviously can't just play more ranked etc without ever having played a role. But here's the thing...how and where do you learn? Sure you can make a custom and learn your clear routes etc..but without a leash you're not exactly getting the jump that you would in a normal game and that would just slow down your clears etc.

You can't just do a bot game...sure that gives you a precursor knowledge...but without an enemy jungler for counter ganks, camps, etc, and the fact that you tossed someone into a 1 v 2 lane and this doesn't give you the experience you need once again to learn the position the way it's meant to be played.

The logical move is to simply jump into a normal game or a team builder as jungle. Here's the problem...the flaming trolls of doom. When you're learning the position for the first time...or even the 20th time...you're going to make some pretty severe basic mistakes. This means there's about an 88% chance you're going to be reported by a troll for being unskilled and them flaming you etc when you're only doing what you're supposed to be doing...learning the damn role.

So what's people's opinion? What is the best way for me to go about learning jungle? I already know "how"...it's the matter of getting the experience of actually playing it and letting the muscle memory work its way up to make me a better player with better map awareness etc. Do you start with a custom and work your way up? Or just jump into a team builder? How did you all do it?