Multiple VPS Nameserver Question

Hello. So currently I have only one VPS but I want to buy more. So I have set for my domain ns1.example.com and ns2.example.com both pointing to my VPS ip. Now I want to get more VPS, but how should I do with the nameservers? ns1.example.com -> pointing to VPS1 IP ns2.example.com -> pointing to VPS2 IP ns3.example.com -> pointing to VPS3 IP
and so on? I only have 8 nameserver slots, so what should I do if I have for instance 10 VPS? And can I use Cloudflare? If yes, how?