I am far from an expert, but:
Depends on what you're looking to do.
If you are able to trade all day you can flip volatile stuff rapidly. That's what brackis/rob mafia etc. play with, I think. If you can't pay attention you can lose your shirt on speculative stuff, but if you've got the stomach for it, and the flexibility to execute on a turn, you can make money pretty quickly.
If you are looking to just buy value and hold onto it, I would suggest mutual funds, or ETF's or an overall market index. Very different types of investment. This is the majority of what I invest in, with only a couple thousand to play around on riskier stuff for fun. If it goes away, it goes away.
I think most online brokers will have a basics of investing as a part of their offering, and many will allow you to play on a simulator...which I would recommend before you start playing with real money.
After learning the basic terminology and types of transactions and you determine what type of investor you are you can target whatever resources are most appropriate to your aims.
Resources for starting:
https://learn.robinhood.com/
https://www.fidelity.com/trading/overview
https://www.tdameritrade.com/education/investment-classes.page
Investopedia has basics for free, and they try to sell you on more advanced concepts through courses.. ameritrade gives free courses.
Some sims:
Investopedia
https://www.investopedia.com/simulator/
Marketwatch
https://www.marketwatch.com/game
wall street survivor
http://www.wallstreetsurvivor.com/