the spray doesn't go everywhere, it's pretty controllable. it will basically only go in the direction you point the airbrush and doesn't spatter. but you'll find that any room you airbrush in regularly will start building up a layer of 'paint dust' from particles in the air settling.
i bought one of these - https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1 to basically suck any over spray out through a window. was £68 but there's also really simple guides on making the same thing out of a box and old PC fans. don't have links but remember seeing them when researching.
the cleaning pot is essential, the brushes are useful. i also found myself using a ton of cotton ear buds for cleaning out the paint bowl (where paint sits in a gravity fed airbrush) when i wanted quick changes of colour without a full disassembly / strip clean. would also recommend buying a big box of cheap latex gloves, because your hands will get covered in paint and it's a pita to clean off entirely. i dunno if you have it included in the paints coming, but you'll also need some masking liquid and/or tape. unless you're planning on only painting things single colours.
i have the Angel Giraldez book, and it's basically very good but i don't know that there's anything you couldn't also find online. don't regret buying it though. not much more to say.