I have to ask if you are asking this question from a character/role-playing perspective, or from a player/numbers perspective? If the latter, then I would probably drop Evocation and Enchantment, keeping the defensive options of the Illusion school open. There are plenty of damaging spells in Necromancy for killing your foes, and some of them have the added bonus of boosting you at the same time.
If you're approaching from a role-playing perspective, I have always stuck by the 2nd Ed. rule of dropping Illusion and Enchantment. My character (Luthien Greyspear, natch) thought those schools were for charlatans and mountebancs, and were too...wispy to be effective. Part of this is because he was originally a 2nd Ed. necromancer, and he had great Wisdom, therefore great saves vs. illusions and charm spells.
In his eyes, it was too wishy-washy to make friends with your enemies, or to hide behind a fake monster and expect them to be scared of it. Just kill them, and THEN put them to work for you. Saves on time, and on payroll expenses.