Depends on what interests you and what your strengths are.
There are lots of investment types out there - real estate, debt, equities, brick & mortar businesses, on-line businesses, etc.
For Americans, I think that real estate and stocks are definitely still ways to gain wealth and become financially independent.
And assure yourself of being able to retire (possibly early if you want) - maybe with a lot of cabbage if you've investing wisely.
But finding ways to make cabbage off the Internet has proven to be quite profitable for loads of folks - so this could be an area to explore, too.
If you have an interest in stocks but not a lot of interest in the details, then stock indices will work just fine.
You invest your money and if the S&P 500 goes up 10% this year, for example then that's about what you'll get (slightly lower).
If you have an interest in outperforming stock indices, then there are plenty of companies to help you do it.
Some have been mentioned earlier.
But those companies are best as long-term investments.
If you're not interested in long-term investing, then those companies won't help as much.
I invest in stocks long-term because I think it's one of the best ways to outperform the stock markets - especially with the amount of time you put into it.
I can go long periods without researching anything and still beat up the stock indices pretty well annually.
However, I do read a lot - 6 newspapers a day or so plus magazines, journals, etc.
More scanning than reading - unless it's an article of interest which seems rare nowadays.
I haven't mentioned specific companies because I don't think that'll help you too much.
Learning where and how to fish rather than be given the fish is a better plan I think ( I shared some things I look for on an earlier page).
I prefer to share general ideas with how I invest, for example so that folks can figure out the specific companies on their own.
Because you may turn out to be a better stock investor than me given time to soak it all in.
So what should I invest in?