I recommend paying more attention to secret societies than to mutations. The secret societies are one of the Gamemaster's most valuable tools for turning players against each other.
For new players, your best choices are pairs of polar enemies: Psion and Anti-Mutant; Frankenstein Destroyers and Corpore Metal; and possibly FCCC-P and PURGE, depending on how violent you want them to get.
Give each player a secret mission that directly conflicts with the mission of at least one other player, such that success is zero-sum (one must lose for another to succeed). Then give each player secret information that at least one teammate belongs to the enemy society. Be sure to hint at prospects for promotion and other great advances if they take the initiative and terminate the enemy teammate.
That should carry you far.