Do you have any idea how much budget do I need to start my own Electrum server and let me know if there is a guide to make a server that includes cloudflare to add a server and protect the server to DDOS attacks?
More/less just like budget required to run Bitcoin full nodes. You can run Bitcoin full nodes + electrum server on Raspberry Pi 3.
I've no idea about cloudflare integration, but there are many ways to protect server from DDoS attack such as block known malicious IP and limit request amount.