I am a devotee of John Bogle, and so my stock investments are a broad index fund... Vanguard Total Stock Market Index... that is instant diversification, low turnover, low dividend yield, and a negligible expense ratio. If you want international exposure (I do not) substitute Vanguard Total World Index...
If you want some bonds, add in the Vanguard Total Bond index...
Most US market measures are near all time highs... it is easy to get overly confident when it seems the market cannot loose, but can you hold your position when the value of your holdings just got cut in half? I held in 2000, 2008, and 2020... but it was gut check touch and go at times... frankly a monkey throwing darts at the Wall Street Journal could have made money post Covid... it is not skill but rather tenacity... "time in the market" not "timing the market" if you will...
Stock market investing is not for the faint of heart, or the dilettante I think myself pretty savvy, and even I do not dabble in individual stock... the information deficit is simply too large, and not in my favor. For every Nvidia there is an Enron...
But in one sense you are correct...
"
The first million is hard, but the second million is inevitable." - Brian Tracy