Are you planning on going for a DPS role or a Tank role? Do you want to focus on stamina or magicka? If you're a Dunmer DK, I'd guess magicka because your race benefits from magicka passives.

For a ranged (staff) magicka DPS, I'd recommend going mostly light armor with a piece or two of either heavy or medium.

For a melee magicka DPS, I'd choose still mostly light with some medium (for stamina) or heavy (if you need health).

For a Tank role (still recommend magicka here), I'd go mostly heavy with some light for magicka.

However, as a level 8 and until you know for sure what armor combo you'll want endgame, you should definitely be wearing "Rainbow Armor" (mix of all 3 armor types) to level up all 3 types so you can have options later on. Wear at least one piece of each of the two armor types you'd want a secondary bonus from and have all the other pieces be whatever type you're most interested in focusing on.