addons to create a good server in gmod?

There are a lot of Addons, everyone chooses to their taste and color)
You can search on this forum, there are many interesting solutions, I once also looked for builds and asked for the best Addons, but in the end I put together my own personal build, not the best, but my own)))

there's probably guides on youtube and the community hub
but I just tested random ones on singleplayer

I recommend going onto darkrp servers and see if there is any addons that you enjoy using then see if they are on the gmodstore as some may be custom if its a bigger server

Most of Zero's addons are the best to start off with. Out of all the Zero addons, I recommend:
Zeros Grow OP (Weed Script)
Zeros Trashman (Trash Script)
Zeros OilRush (OilScript)
Zeros MethLab (Drug Script)
Zeros RetroMiner (Mining Script)
Zero's Fruit Slicer ? (Food Script)
It is best to hold this job stuff off until you have the basic sorted out.