I want to be a 1000 year old vampire, and get there as quickly as possible.
The archetype of the being who has fought in revolutions, created inventions, and seen and experienced an impossible amount of things isn't one that is wholly fictional.
People like Da Vinci, Newton, and John Von Neumann fit an overwhelming blaze of activity into single lifetimes, transformed whole fields (or multiple fields), and would be a hell of a party guest.
I won't claim to be an expert on any of the above people, or to have a deep knowledge of how people become polymaths. But it seems that the promising path to walk in the steps of such men is to get close to "the metal" of reality.
Leonardo wanted to learn how to paint better, so he learned anatomy. He understood it in a visceral way that can't be learned from a textbook. Newton hungered for truth, so he dove into astrology and biblical chronology, thinking for himself. (And invented calculus, which he seems to have been substantially less interested in).
Von Neumann was potentially one of the smartest men to ever live. He started game theory as a mathematical field, worked on the Manhattan project, and is revered as a founder of computer science. He also literally created the field of cellular automata on graph paper. I can't emphasize enough how insane that is. Oh, and he came up with the idea of the Singularity, and was one of the discoverers of the idea of Mutually Assured Destruction.
Obviously, these were minds that were easily one in a million (potentially far higher out of distribution, especially for Neumann).
But it seems that diving deeply into solving real problems in a variety of fields is the fastest way to move. For this, it looks like it is necessary to understand each part of the project, if not to do it yourself. If one is learning how radio works, you should know the math, and build it on your bench with wire and razor blades, rather than just reading about how to turn on a ham.
There's a lot to experience in life. And it seems like hopping straight into out of unusual experiences is the best way to do it.
So learn fire juggling! Cook haute French cuisine! Hammer a blade out of rock, and throat sing!
Deep drinkly out of the cup of life, so that you can have lived a thousand lifetimes within your own.
Even a thousand year old vampire, with the wrong attitude, could have lived a life full of nothing but television and accounting. There might not be a right and wrong between the vampire of myth that has the strength and wisdom of a hundred men and his accountant counterpart. But I know which I'd prefer to be.
As Robert Heinlein said:
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.