Well I would suggest being a Khajiit or a Bosmer The starting stats for Khajiit are things like one handed and sneak. Bosmer's are archery and sneak (depends which type of assassin you'd want to be). Conjuration is pretty easy to level up, seeing as my Khajiit is heading up there pretty quickly. When you choose your first standing stone, go for the mage one, but make it a goal to get to the lover stone (learn all skills a little faster). You might want to work on the stealth, archery, one handed, and conjuration skill trees to begin with, but broaden your horizons, maybe putting some perks in for enchanting as well (I have a bow that draws out the life of my enemies just in case the first hit doesn't kill them).