I use Interactive Brokers; tremendous execution with very low rates. As to how I, or anyone else, picks stocks there are entire books devoted to that question, but there is no one right answer.
How much risk do you want to take?
What are your goals?
What edge do you have, meaning do you have an area of expertise where you know more about an industry than the average person?
The considerations for how much to invest and what to invest in are numerous. Only you can decide what is right for you, but I will leave you with some thoughts. Just because the shares of a company are low does not mean they are cheap. I don't fully buy into Efficient Market Theory, but there is some truth to it and a stock selling for pennies is there for a reason.
Fast moving stocks can move fast in both directions. Yeah, it's great when they're going up, but..... Still, if it fits your risk profile then go for it; I'm not trying to dissuade you, but do believe that buying stocks for the "interesting" factor is a path to sub par returns. I've spent my career investing to make money and what's interesting to me is that I no longer have to work because I can support my family with the income my investments earn.
How to do that didn't happen overnight, but I eventually settled into a protocol that works for me. Almost all of my investments have a certain profile and that's what I stay with. I don't need to catch every winner because there are plenty of fish in the proverbial sea and for me to venture into industries that I know nothing about means that I'm involved in a situation where others know a lot more than I do. Over the long haul that's no way to make money.
I wish you well and hope that you achieve the results you want.
I'm here not because I've lost everything, but because I have so much to lose. ~ Taken from a poster on SR.