I am making a spellsword that uses a 1H sword in one hand and cloak spell in the other. Which armor should I use for him? What armor do you usually use for a spellsword?

Light.

Gives protection but doesn't drain on too much stamina allowing a good balance for magicka.

Spellswords can support armor with spells in alteration, restoration and conjuration. Unlike a maxed out warrior who would be low in magicka but high in carrying strength and stamina.