Robinhood is a good place to start. If you planning long term investing. Put most of the stocks on reputed companies such as Apple , google , amazon etc.
Also , put some money in companies that you think will be big in futures.
I do not suggest investing money on pharmacy / oil ....not if you are planning to get a good night of sleep.

Look into cryptocurrencies as well, I believe they are the future. The crypto market is very speculative and volatile right now ....but I think its still worth the risk. Crypto is the internet 2.0 and has the capability to disrupt or at least change the financial game.