There are many on line services for stock research and many fund families such as Fidelity, mentioned by Cobra or Vanguard
https://flagship.vanguard.com/VGApp/hnw/HomepageOverview that offer valuable data.
Fund families such as Vanguard and Fidelity offer a very broad variety of individual funds in which you may invest. The sites also provide performance data of each fund.
The investment vehicle you choose is often governed by your age or investment philosophy, high risk or low risk. Peronally even though I am 63 years old I am still invested aggressively. I am in a gold fund, MIDSX, a Russian fund, LETRX, a energy fund, VGENX, a real estate fund,CSRSX and a few others. Almost all considered aggressive or high risk, not what an investment counselor would advise.
As for research I uses the funds web sites themselves and also subscribe to Morningstar. My guidelines are,
in most cases, to invest in a fund that has a good 5- 10 year history.
I am not smart enough to figure it out for my self so I depend on data. As the old saying goes "In God we trust, all others bring data"

How much to invest?
Right now I invest with my employer the max amount allowed by an IRA, I think it either 14 or 17%. Don't know exact without doing the math.
Historically I haved saved at least 10% of my salary even with kids in college. Did have to tap it a few times like for my daughters wedding and some stock options.
Most advisors will suggest 10% and if your company matches contributions you are just plain stupid if you don't contribute to at least the matching amount.....that's
free money.
And yes there are some who don't. Calling them Numbskulls would be coplimentary. And yes I knew one, took me three years to convince him he was stupid. Then he lived with regret for the three years he lost by not contributing.

I also did not start saving wisely until in my 40's but the increase has been significant. If someone starts saving wisely in their twenties it is quite likely by 50 they will have no need to work except for personal satisfaction.
Pay attention to investing and saving, too many working class people do not.