Super new to investing - looking for where to invest, and what platform to use.

I’ve seen cashapp, robinhood, acorns, and several other apps. Which one do I use? And what stocks do I buy into? I’d like to make some risks and make some safe investments, due to the fact that I’m young. I also want to invest into something for my kids, but don’t know where to start. Trying to stay low budget (I’m a single dad) so please, give me your suggestions!