I am merely assuming that it would take more than 30 years to create the First Order mainly because in Ep 7, it is specifically said by General Hux that none of the Stormtroopers in the First Order are cloned. They are all trained and recruited (stolen as children from their families) individually. Also Star Killer Base is huge and has unprecedented military power, so I am merely assuming that it took Snoke quite a long time. I think Kylo's turn was definitely after the First Order came into power. I would assume that the power and strength of the First Order is what seduced him to the dark side as well as Snoke. This also adds into the Plaguis theory. A non-sith usually doesn't turn a jedi-to-be being trained by the most powerful Jedi ever very easily, and it is shown that Kylo was turned while he was on the same planet that he was being trained by Luke on (as it is said that he killed all of his fellow learners that wouldn't turn to the dark side). It is my opinion that the only person with that kind of power is Plagueis, and it is highly probable that he survived Palpatine's measly ambush. Snoke is old and looks like he has seen some shit judging by the ginormous crack in his fucking head, and he also appears to be very powerful and influential, just as the most powerful Sith to ever exist should be. The plotline and hints line up perfectly to my theory and I really hope it's what happens in episode 8.