Vanguard FTSE Global All Cap Index Fund

https://www.mrmoneymustache.com/2011/04/10/post-4-what-am-i-...

Look up Bogleheads and Lazy Portfolio.

I think if you have a genuine interest in this topic and some basic understanding of maths (probability, etc.), textbooks can be quite accessible. Read, for example, "Coporate Finance" by Berk and DeMarzo or have a look at the CFA study material.