I am just a self taught investor over the last 25 years.
I most certainly don’t know it all, and have had my fingers burnt at times.your reasons).
All my funds/shares are in tax free wrappers, funds are dealt for free, shares at about £12 a deal.
My don’t want a complex portfolio that needs attention every few days, as I am a big traveller/adventurer and often busy for extended periods without an internet connection.
With this in mind, I am keen on a bias of steady growth (rather than short term fast movers).
I am not keen on any sort of single industry funds/ETFs (eg IT or AI focused funds), as these grow fast and then die fast (I had my fingers burnt in the 2nd dot com bubble in the early 2000s).