What should I do to secure Debian for everyday use and gaming?

Start with the basics rather than installing a pile of security tools. Keep Debian and your applications updated, use a normal account for daily work, and only grant administrator privileges when you need them. Stick to trusted package sources and be cautious with scripts that ask to run as root.

Debian receives security updates for supported releases, so an older application version number doesn't necessarily mean it has missed every security fix. Make sure security updates are enabled and apply them regularly.

Debian has firewall capabilities, even if you don't see a Windows-style firewall interface. UFW is a relatively straightforward way to manage rules. You can install it with sudo apt install ufw, then check its status and configure it before enabling it.

Also check what services are listening for connections. A firewall is useful, but it doesn't replace disabling network services you don't need.

Consider LUKS disk encryption during installation, especially for a laptop. It helps protect data if someone gets the powered-off machine or removes the drive. It won't protect an unlocked system from malware or someone using your account.

You don't necessarily need antivirus as your first step on a Debian desktop. ClamAV is an option for scanning files, while AIDE can help detect changes to files. Neither replaces updates, sensible permissions, or care with downloads.

Mandatory access controls such as SELinux are another layer, but configuring them takes work. Get comfortable with the basics before adding controls you aren't prepared to maintain.

Debian is a reasonable choice for daily use. Its stable release favors older package versions, which can matter if you want newer gaming software or hardware support. Fedora or Arch may be worth considering if newer packages are a priority.

Kali and other security-focused distributions are aimed at different tasks. You don't need one just to have a secure everyday desktop.