dude thank you so much, I still haven't been able to find a right guide. This is the only info I got so far.
I found this guide but it needs the assettocorsa.exe to launch. I can't install a full on game on a dedicated standalone server which confuses me.
I feel your frustration and have been going nuts trying to figure out how to run a server on a dedicated PC. First off, don't download the dedicated server from Steam as it will require Steam to run the server and will require Assetto to run. Go to the Assetto folder "Server" and use the AC Server in there. After opening Server Manger, 1st thing you'll want to do is click on the Update Server Content. After this, setup your server settings using Server Manager. Name each server name different and they will be saved in the "Preset Folder".
Setup your router to forward port 9600 for UDP/TCP, incoming and outgoing.
If your router has a HTTP option, set this to port 8081 If setting up multiple servers, you only have to do this once.
After you get all your server game settings setup, copy the entire "server" folder over to a dedicated PC.
To pick which setup to go with, go to the "Preset" folder, select which server config you want to run and copy the entry list and server config files to the CFG folder. Make sure to delete the current files in CFG folder.
After you have the preset files in the CFG folder, you can launch your server using the ACserver application.
You cannot use Assetto Corsa Server Manger on the dedicated server PC. Easiest thing to do is use it on the main computer and create server presets. Then copy only the new presets to the server PC.
If you want to run multiple servers, copy the "Server" folder from the main PC to the dedicated PC. Then rename the ACserver application by putting a # at the end of the app name. I.e. Acserver2
You'll have to switch the UDP/TCP port in the server config file (open this file with notepad) and create a new TCP/UDP rule in your router. The factory preset is 9600 for both. I set my new server to listen to 27015 for both ports. I created 2 more servers using 27020 and 27025.