These days a Nasdaq ETF is likely the best bet (it's what I use in my IRA) since it has been conistently outperforming the S&P 500.

I'd be cautious with the more exotic leveraged ETF. Instead, for my non-investment accounts I've been mostly holding the Mag 7 since last year (after rotating out of pandemic stocks following the rebound). I shared my results over the last couple of years on by blog where I document my thinking for future reference/improvement (https://gmays.com/2-year-follow-up-on-buying-the-dip-on-pand...). My current IRR from that portfolio is 83.70% over the last couple years for context.