Could use some suggestion on how to build my thief character. Is stamina important? I'm also not sure about what fighting style to approach. I'd like to do the sneaky surprise attacks, but from my other characters and what I've seen with them, I think there are situations where pure stealth will not be very helpful, especially when it comes to boss encounters including minions. (Maybe even without.)
I'm trying to go for dual daggers right now. Any spells I should look out for? What would you consider a good magicka/health/stamina ratio?
No i would say go health and nothing else. If you don't mind giving yourself an early advantage get the dark brotherhood armor, it's very nice, and will make your life so much easier. Dont spread yourself too thin skills wise, if you level up fast then so does your enemies. If you do like the sneaky approach then obviously you need to level stealth more then anything. Best way of doing that is successful sneak attacks, as you get a stealth gain virtually every time you sneak attack (at low'ish level).
I finally gave in and picked up archery to use when there just is no way to make use of your sneak attack. Good archery perks are powershot and ranger, as they make you almost invincible, though quick draw is excellent too. As for your 1h skill, so far i just put points into armsman (is that the right name?) and leveled the skill for high base damage. The X30 multiplier takes case of rest (with the shrouded gloves from DB set)
Im level 25ish now on master with my Kajit and have not encountered anything too difficult, after i picked up archery as suppliment to daggers. Hope it helps a little.