If your PC is incapable of running 3v3 AIs at at least one simspeed consistently (See your score panel to check your simspeed), please do us a favor, no matter what gigabit Internet connection you have, 50 ping or less, it will lag the hell of out of others.
I have joint 3 3v3 custom games when hosts specified 150< ping. Everyone did have 150 or less ping, but games all lagged. There was always 1 or 2 people runnign at 0 or -1 Simspeed, dragging everyone to a snails game pace.
Please, if your PC is incapable, do not join large games. Tune down your game quality settings, turn off FSAA, AF in your graphics card driver. Then go single player to test which maps, number of AIs your system can handle without slowdown before joining game online and ruins the fun for everyone.
Thank you very much.