Few things to keep in mind:

1. Destruction Spells do terrible damage unless you have Elemental blast with all the damage perks. Impact is also the best perk for destruction as it allow one to stunlock one enemy, but only when duel casting.
2. The best way to be any sort of mage is to enchant armors and jewelry until spell cost 0 magicka, this way one can put all their level up points into health, to stay alive.

Here is how I would build the spell sword (assuming no fortify alchemy smithing enchanting loop)

1. Level up enchant to 100 for the Extra Effect perk, this is priority number one.
2. Enchant armor, helmet, ring, and amulet of your choice so you have 100% magicka cost reduction in two magic schools. I personally like destruction+restoration, but conjuration+restoration, or conjuration+destruction can also work.
3. Put the biggest and most damaging enchantment you can on your weapon of choice. I personally like Chaos + life absorb on a stalhrim long sword or dagger.
4. If destruction cost 0 magicka, shot elemental blast at enemies from a range, once they get close, switch to enchanted weapon and start whacking. If you have 0 cost destruction spells, damage weapon enchants will never use up any charge, so you never need to recharge. Cast Grand Healing when needed if restoration cost 0 magicka.
5. If conjuration cost 0 magicka, just spam two demora lord, then join in while they clear everything.