Your basic requirements are:

• Some kind of domain / subdomain payed or free;
• Home ISP that has provides public IP addresses - No CGNAT BS;
• Ideally a static IP at home, but you can do just fine with a dynamic DNS service such as https://freedns.afraid.org/ (will update your domain with your dynamic IP when it changes);
• Ideally a home ISP that allows for "bridged" mode or has a ONT device + router where you can add a switch in between and have the server directly connected to the Internet, with its own public IP, outside of your home network (more bellow);

Hardware coices:

Don’t get server hardware, use regular desktop/laptop machines as they’ll be more than enough for you. Server hardware is way more expensive and won’t be of any advantage. If you’re looking to buy you can even get very good 9-10th gen Intel CPUs and motherboards that are perfect to run servers (very high performance) but that people don’t want because they aren’t good to play the latest games.

This hardware is also way more power efficient and sometimes even more powerful than any server hardware that you might get for the same price. Get this hardware for cheap and enjoy.

If you don't require a TON of computer power some people might suggest ARM board, such as the Raspberry Pi, but be careful with those. ARM is great for power savings but compared to consumer hardware is it shit when it comes to performance and reliability. Also I personally like to avoid the Raspberry Pi and their stuff as much as possible. They've done good things for the community however they've some predatory tactics and shenanigans that aren't cool. Here a few examples of what people usually fail to see:

• Requires a special tool to flash. In the past it was all about getting a image and using etcher, dd or wtv to flash it into a card, now they're pushing people to use Raspberry Pi Imager. Without it you won't be able to easily disable telemetry and/or login via network out of the box;
• Includes telemetry;
• No alternative open Debian based OS such as Armbian (only the Ubuntu variant);
• Raspberry Pi 5 finally has PCI. But instead of doing what was right they decided to include some proprietary bullshit connector that requires yet another board made by them. For those who are unware other SBC manufacturers simply include a standard PCI slot OR a standard NVME M2 slot. Both great option as hardware for them is common and cheap;
• It is overpriced and behind times.

For what's worth the NanoPi M4 released in 2018 with a RK3399 already had a PCI interface, 4GB of RAM and whatnot and was cheaper than the Raspberry Pi 3 Model B+ from the same year that had Ethernet shared with the USB bus. If you still want ARM and you're about just serving a few websites, cloud service wtv pick a Chinese brand such as friendlyelec or rockpi. More computing for less money and a lot less proprietary BS.

Mini computers from big brands though, for 100€ you can get an HP Mini with an i5 8th gen + 16GB of ram + 256GB NVME that obviously has a case, a LOT of I/O, PCI (m2) comes with a power adapter and more importantly it outperforms a RPi5 in all possible ways. Note that the RPi5 8GB of ram will cost you 80€ + case + power adapter + bullshit pci adapter + sd card + whatever else money grab.

Side not on alternative brands, HP mini units are reliable the BIOS is good and things work. Now the trendy MINISFORUM is cool however their BIOS come out of the factory with wired bugs and the hardware isn't as reliable - missing ESD protection on USB in some models and whatnot.

Quick check list for outward facing servers:

1. Isolate them from your main network. If possible have then on a different public IP either using a VLAN or better yet with an entire physical network just for that - avoids VLAN hopping attacks and DDoS attacks to the server that will also take your internet down;
2. If you're using VLANs then configure your switch properly. Decent switches allows you to restrict the WebUI to a certain VLAN / physical port - this will make sure if your server is hacked they won't be able to access the Switch's UI and reconfigure their own port to access the entire network. Note that cheap TP-Link switches usually don't have a way to specify this;
3. Only expose required services (nginx, game server, program x) to the Internet. Everything else such as SSH, configuration interfaces and whatnot can be moved to another private network and/or a WireGuard VPN you can connect to when you want to manage the server;
4. Use custom ports with 5 digits for everything - something like 23901 (up to 65535) to make your service(s) harder to find;
5. Disable IPv6? Might be easier than dealing with a dual stack firewall and/or other complexities;
6. Use nftables / iptables / another firewall and set it to drop everything but those ports you need for services and management VPN access to work - 10 minute guide;
7. Use your firewall to restrict what countries are allowed to access your server. If you're just doing it for a few friends only allow incoming connection from your country (https://wiki.nftables.org/wiki-nftables/index.php/GeoIP_matching)

Realistically speaking if you're doing this just for a few friends why not require them to access the server through WireGuard VPN? This will reduce the risk a LOT and won't probably impact the performance. This is a decent setup guide https://www.digitalocean.com/community/tutorials/how-to-set-up-wireguard-on-debian-11 and you might use this GUI to add/remove clients easily https://github.com/ngoduykhanh/wireguard-ui