The simplest is following the Bogle three fund method VTSAX / VTIAX and VBTLX from vanguard that have a low fee split to your liking. I weight towards us stocks and very little in bonds. If you just did this over the last few years you portfolio would be up now , might have been down last October but over all doing ok. I auto invest in these and then go into single stocks I think are under valued. The books by Peter Lynch were easy and fun reads about investing although you can also get the main points watching a few of his videos on cspan for good information on trading that’s relevant today.