Well, i dont like to give warn for first time and i wont do it in future also that is what i do if they just invite their friend to another in main Mute->Kick->warn->Ban and if player keep spamming and inviting all players to other server then first mute and if he kept doing it then warn and after that a 7 days ban and about warns we do it on reports because we cant mute offline players
it depends on situation and you wont understand