QQQ, the NASDAQ 100 ETF, has done very well in recent years but I don't own much of it. Mostly it's done well because Apple accounts for about 13% of it.
It's hard to beat SPY, the plain vanilla S&P 500 ETF. I started with Vanguard Total Stock Market Index fund years ago. That's a traditional mutual fund that covers about every stock there is (except OTC/Pink garbage).
I also have some DIA (diamonds), a Dow 30 Index. It has a fair holding in Boeing stock of course.