I think there's a lot of flappers on here. Stones is good enough - he was good enough last season and the season before. He's had rotten luck with injuries and he needs a commanding CB next to him to blossom, which he currently doesn't have. Laporte isn't gone forever.
Someone said Mahrez isn't the player we need him to be - for real? Mahrez is class! more than justified his place in this team on a number of occasions, someone mentioned the same about Jesus - again, class player that deserves to be here.
I think we need:
one CB to replace Vinny and the possibly outgoing (and ageing) Nico, then one of either THB or Garcia promoted.
a left back to support Zinchenko, as Mendy has proven nothing and Angelino, regrettably, doesn't look like a champion
a winger to replace Sane IF he leaves
a striker to prepare for Sergio leaving.
thats it! Foden will naturally replace David, and he'll get more games as the season progresses. People seem to think he needs to be on the pitch with Silva to learn from him and prepare, this isn't true.
so in summary I'd suggest two signings for now, a CB & a LB, and then a winger and a striker in the summer or next.