What should I buy to set up multi room wireless

Okay, another question. What amp(s) or other things do I need to make all this stuff work?

Everything you need is listed on my recommendations above other than speaker wire to connect the outdoor speakers to the Sonos Amp and a wireless router to connect everything to your Wi-Fi network.

Great! No amp required.

I forgot to ask: Can I stream my music library files from my phone or a cloud service like Google or One Drive?

If you have an iOS device like an iPhone, iPad, or Mac, you can play music from those devices using AirPlay. https://support.sonos.com/s/article/1230?language=en_US

You can also set up the Sonos app to play music from your personal music library stored on a Mac, PC, or NAS drive. https://support.sonos.com/s/article/257?language=en_US

You could also upload your personal music library on YouTube Music and play your library either from the YouTube Music app or through the YouTube Music service on the Sonos app. https://support.sonos.com/s/article/3259?language=en_US

That’s great. I store my music library on my computer and also on One Drive, so I should be able to access it with Sonos. Thanks again!

should you become tight on budget then you might also consider IKEA’s SYMFONISK - I use them for my office and bedroom - the sound quality is less than a SONOS ONE or ONE SL, but this is justified by the price tag (sells for about 119€)