Assume that the future can change based on your actions, so any historical information that you bring along with you from the intervening 25 years may quickly drift out of the new realities history.
Edit: also assume that you can be given a healthy 21-year-old body if you want or take your previous self’s place.
Further, identification will be provided for you if you were not born at that time.
I would bring a laptop with a good CPU and GPU, an ASIC Bitcoin miner and 10,000 in cash in case for some reason the miner broke or didn’t work.
I would bide my time at pizza delivery jobs for 10 years paying rent living on ramen and buying small amounts of gold and silver coins. As soon as the first btc client was released by Satoshi I would start mining. I would be selling things on the cheap and performing services as much as humanly possibly. Id have a small gold and silver for BTC company, selling $50 gold coins for the equivalent of $25 in BTC at the time. I would not stop until I had at least 1,000,000 Bitcoin, or January 2017, whatever came first. As soon as the BTC rush of 2017 starts, I start selling my BTC en masse at the peak. Mail order, cash, in person, whatever. Claim what I need to on taxes. Sell the rest via an exchange before it’s regulated as a security and needs to be taxed.
Now I am a big time multi-billionaire and no one even knows my name besides my financial advisors and closest friends from my pizza delivery days who now work for me doing “whatever the fuck they want” work for 100k per year.
I keep investing in companies who sell the most in online communications services (zoom, Microsoft, etc), mask production, hand sanitizer, laptops, gold and silver, and whatever else I can remember. As a ride out COVID, I’ve increased my 5-10 billion to 20-30 billion.
Now I live a happy “do whatever the fuck I want” life at roughly the same age I am now, only now I have total freedom and power because of "20 years of hard work and foresight – I started as a pizza delivery boy, and you can too ;).”