yes, robinhood is still not released but you can sign up and wait for invitation.
penny stocks are never for long term. It depends how much money you are pouring into stocks and how much weight does that put on you. For some people loosing 10k is nothing, for some it is several years of saving. So, you can play penny stocks with money you would think you already lost the time when you put into those stocks.
As an example I invested on couple of chinese stocks back in 2011. It was hot then, and I read lots of articles and yahoo forum (bullsh*t), where lots of guys were updating on how great the companies were how they were doing business in China. Spent a lot of time, and convinced myself to buy those. But lost 99.99% on one, and 89% on another. They were some company dealing with minerals and energy bulbs. Chinese stocks are past now, but even all penny stocks are risky. I would suggest to invest on mid or small caps, may be couple dollars or more, and always look at average volume, otherwise you could be buying stock at real cheap but never evere be able to sell them even cheaper. Make sure there are lots of people trading or watching those stocks, based on daily volume and people posting in stocktwits. Give it a year or so on learning before you finally put your huge savings into stocks.