Starnet is a must if you want AIs that actually do something (although in MP that may not be necessary). ACEMOD is a must if you want the Crisis to be a challenge. For auto-pop migration, I would recommend a combination of free GTOS (Pancakelord has a mod on the workshop that does that, but it's trivially easy to make yourself if you want) and my No Performance Hit Auto-Pop Migration (also on the workshop), since these have minimal performance impacts. That being said, both of these make the game slightly easier (no energy cost for resettlement) and have a hole wherein non-full citizen (enslaved or servitude) robots aren't resettled (unaffected by immigration and GTOS), so if the host has a good machine you may want something else.
Another mod I'd highly recommend is the Enigmatic Fortress 2.6/2.7 (still works for 2.8) fix, so that the EF doesn't break your game (worse in multiplayer than in single player, since there's no console for fixing it).
