Re: what safety things do i need in my boat?
Check your state requirements and possibly Coast Guard for requirements.
I'd add a throwable cushion or two, a mirror wouldn't be bad, FE for sure (sized for your boat), I'd skip the flare gun, an alternate method of bailing out (a bucket or old sauce pan), perhaps an oar or two (depending upon boat), and a boat hook.
You didn't say what rivers. If you are talking about the Ohio or Mississippi, versus a smaller slower river, you may also want river charts and become familiar with the various navigation markers.