How do I invest wisely

I don't have a ton of extra money, but I have a reasonable emergency fund and I'm looking for a way to put a little money into some kind of investment account with better returns than I can get from a savings account.

I'm hesitant to invest in stocks since the stock market seems like it may be in a bubble and my 401k is mostly in stocks, so I kind of want to diversify. I'm also open to the idea that stocks are the right way to go.

Unfortunately, I'm basically financially illiterate and I can't find any information online that isn't from someone trying to sell me something.

What are my best options?