The really important thing is knowledge, and having a correct understanding of how the world works. And then you'll need some work, hard work even, and a bit of luck, but you will succeed if you try enough times. As long as you have the knowledge.
Which is why IF Bill Gates, warren buffet, *insert most selfmade rich people here* were too lose all their wealth and contacts, they can probably become rich again given enough time. Perhaps they won't become as rich as they were, because they got really lucky the first time. But they'll be a lot better off than the average person for sure.
What type of knowledge tho? I know people that know a lot of things, but they aren't pricessely right. Then I look around, and all I see footballers, boxers, celebrities, making millions, then the occasional guy that creates a viral videogame and becomes rich overnight over google adsense revenue and whatnot.