Hosting a private server

You could port forward it, but usually that is a pain in the ass.

First let's find your default gateway by opening command prompt as admin and typing this in, 'ipconfig' Like this,
https://gyazo .com/5fc00b37ac1e2f14b0cf7da93933aaf2

After that look around until you see "Default Gateway" it will look something like this,
https://gyazo .com/8ffc03759f308c2e94a58c2343c3f4e3

Then open up your browser and paste it in, so in my case i would just put 192.168.1.1 in my browser.
https://gyazo .com/eb278002ecb09c6934191ae27f196bbd
After that login to your router and look around for your firewall settings.

The way I do it, I just make myself a DMZ host because i'm too lazy to port forward
Once you find your DMZ host settings, make sure it's enabled and then go back to command prompt and find your IPV4 address.
https://gyazo .com/f3fad1773b2b75ea1c2bf95c85eaa87c

So in my case I would set a DMZ host to 192.168.1.7 like this.
https://gyazo .com/34ea24001f449c1d826e2e534f740e5b

Then press Apply and go into garrysmod.
If you used this method simple press start new game and make sure to set the number of players and a password by doing sv_password in console or in the main menu where you select the map you want to play on
They can play with you by finding your game in the gamemode section or if you send them your IP which you can find my typing 'what is my ip' in google.
If they want to connect via ip then they need to enable console and type in 'connect ip'

you should still be able to use hamachi

Yeah they could, they just need to do sv_lan 0 in console when they're in a game.