lily,
its quite common that tbf babies dont poo every day. Just be prepared that on the poo days, it will be A LOT of poo! oh yes, use a changing mat.
On one of my bb poo days, there's so much poo that it totally cover the whole diaper from front to back. When I open the diaper, I got a shocked, then close it back and ask my mum for help cos I dont know where to start cleaning! BTW, fitti basic is quite good also and there's no leak.