I'm not an expert, and I don't want to rain on your paradise, but it probably won't matter. Unless you're a very early employee at a start up that would become very large, you're probably not gonna get rich from the equity. You trying to pick such a start up to become part of is a harder problem than VCs trying to pick one to invest in because everybody wants money but not everybody wants an employee. So rather than working your little butt off for the next 2 to 5 years with the hope of making these guys rich so that you get some trickle down riches, get your nice payday upfront and if you want to get rich from start ups start one yourself.

The core points of working at a startup are: freedom, people you meet, the resume creds, the experience. That's what you really get.