I've used Robinhood, it's really easy and you can get started with low value stocks and then work your way up to investing more money when you get more comfortable using the product. It's as secure as your banking app, the only real downside is that it's not really made for day-trading due to the turnaround time (2-3 days I believe) of buying stocks. Also, Coinbase app if you're interested in investing some money into Bitcoin : )
