Never done it before so here are some Q's if you guys have time to answer.

Does light or heavy armor reduce my ability to use any kind of magic? If yes how?

If spell description says; Creatures and people up to level 6 will attack anything nearby for 30 seconds. How do i know what level my opponent/creature is? Is this spell tied to my level somehow?

Is dual casting perks worth it? currently i have flame on one hand and frost spell in other hand and my character seems to do more than enough damage when i use them at the same time.

When i use spell that works for a certain time say, 30 sec or 60sec, is there some secret way to know when the spell effect wears off? in oblivion we had those small icons in top left hand corner if i remember correctly.

Light and heavy don't reduce your ability to use magic, but robes generally have more beneficial bonuses to the leveling wizard character. Archmage robes are insanely useful to have while leveling up, as is Morokei.

As for level, most humanoid opponents are either around your level or below you, so you can mostly use your own level to determine that. For animals on the surface, they mostly have static levels. Giants are 36 and mammoths are 42 I believe.

Dual casting is worthwhile for specific spell schools. Destruction dual cast allows you to stagger enemies, and illusion dual casting allows illusion to remain viable at higher level (since a dual casted illusion spell more than doubles the level that spell can effect).

When a spell will wear off... mage armor has a visual effect on the screen when it wears off. I don't think there is tracking off offensive debuffs, but you can check active effects to see what spells you are under the influence of.

Thanks man, i'll prolly go with the light armor since it does not affect effectiveness of a spells and i can add magic regen effects on regular armor aswell.

The mana regen you get on armor is small compared to the mana regen on robes.

This is absolutely true. But regen is fairly worthless anyway. It's better to enchant for fortification of magic schools. With a heavy enchant investment, this will beat robes.

The only problem with armor is Alteration armor spells. Make sure if your wearing armor not to take the "Mage armor" perk in Alteration.

Right, you might be better off using robes for regen and fortify and using alteration as your defense, you can get a fairly high armor rating using mage armor perks early on

I prefer using no armor. Alteration mage armor perks work, and armor is just added weight that could be used to lug around more loot like more soul gems and potions. And eventually the master level Alteration spell Dragonhide gives you temporary 80% resistance to physical damage which is pretty sweet.

The game will tell you if a spell doesn't work on an opponent. After you cast it a message will pop up saying "enemy is too powerful for (spell name)" If no message pops up, then it means the spell worked. All spells have visual effects that wear off after the duration is over. But watch out, Illusion spells like Fury and Frenzy only work best if you cast it on a baddie from far away, because if they know you're there, chances are just as good that they'll keep attacking you as attack someone else.