$5

@lostnuggets + Acorns

I've been using this app for a couple months and it really simplifies saving/investing. They have a "round up" feature that, if enabled, takes a little bit from your main checking/bank account with each purchase you make and lets you save/invest money really passively. You can set the amount you want to save through round ups and they give a few options with how you want to invest the money. They're kind of cagey with the specifics of stocks/bonds your money gets invested in, but so far the returns I've seen have been pretty decent. It takes a $5 deposit to get the sign up bonus and you can either invest with that amount or withdraw it in 30 days.