Bogleheads wiki and forum has good information and knowledgeable forum participants.
https://www.bogleheads.org/wiki/Main_Page
In addition, following books will give you good fundamental understanding of why and what of investing.
Your Money or Your Life, Vicki Robbins ...
Millionaire Next Door, Thomas Stanley
A Random Walk Down Wall Street, Burton Malkiel
Personally, 95% of my investment portfolio is in Index Funds/ETF. The other 5% I use as play money that keeps me engaged in investing, finance, and trying out new strategies and investments.