Invading the enemy jungle

I've been playing jungle for a relatively long time, and I would like to really start learning how to invade the enemy jungler. Note that this is different from counter-jungling. Counter-jungling is when you go into the enemy jungle with the intent to take the jungler's camps. Invading is when the jungler is the camp your looking to steal ;) . Is anyone familiar with any general guides for how to do this effectively whilst minimizing risks, or would be interested in providing some tips below? I've only pulled it off successfully once before on purpose, but even then I had to wait quite a long time before I could jump the enemy jungler. One of the key things I'm missing currently is a strong knowledge of whom I can invade against. Amumu and Fiddle are pretty obvious, as they require starting at blue buff which means you can catch them at their red. But who else? Rengar should be pretty easy as he starts red almost ubiquitously and gets pretty (read "extremely") low on his first clear, but I also know that a lot of junglers don't optimize their first clear and will thus have to go back before they can even grab blue with Rengar, making waiting at his blue a potential waste. Etc., etc. If you guys could provide any assisstance with either of these points it would be a massive help. Thanks in advance and have a wonderful day :) (unless you happen to face me in-game)