Hey - I'm the pack dev for Magiculture 2 and I just found this thread by searching "magiculture" - sorry to have not responded sooner. In the case of M2, I've added server pack downloads for each version - go to the minecraft.curseforge modpack page and click on the most recent version, and there should be an additional file there called "server pack". Download this, unzip it somewhere on your PC, and follow the instructions in the readme file to to run the server. If you want to play with friends, you might need to port forward or use hamachi. If you want to update the server, download the server pack for the newest update and simply move your world file over from the old one (or alternatively, replace the forge.jar as well as the "mods", "config", "scripts", and "structures" folders with the newly downloaded ones).
If you are looking to start a server for a modpack with no server pack downloads, things will be MUCH harder. Here's the basic rundown:
You'll first have to find out what version of forge the pack uses - download that version from the forge site and choose "install server".
Now, go to the files of the pack you are looking to use and copy the "mods" and "config" folders over to your new server folder. Many mods will also add additional folders that you will need to copy over - for example, any pack with crafttweaker will add a "scripts" folder and any pack with recurrent complex will add a "structures" folder. This might require a bit of research and trial-and-error on your part.
Go into the "mods" folder in your server directory and manually delete every client-side only mod. This will also require a lot of trial-and-error, for sure. I would keep a list of all such mods in a text file somewhere, because you will need to do this every time you want to update the server. (Common examples: Optifine, Dynamic Lights, Better Foliage, Dynamic Surroundings, Batty Coords Mod)
Make an executable .bat file which runs your forge.jar file with increased ram - there are lots of tutorials of how to do this online if you search around a bit. Test different amounts but this is ultimately dependent on how large the pack is and how many people will be playing at a time.
Run your server (don't forget to change EULA to true) and see if it crashes - if it does, check the generated crashlog to see if it was from a non-removed client-only mod or if it was from some mod which is simply incompatible with multiplayer. If the latter is the case, then you may be SOL. Often, there is a reason why a given modpack does not have proper multiplayer support.
Good luck getting your sever started! Hopefully that helps answer some of your questions. Sorry to bring back a thread a month and a half later, but if someone who has a similar question is searching I would like them to find an answer.