I just started a new character and would like to know how to divide my resources like for example: HP: 400 Magika: 400 Stamina: 200
I want to do that but don't know if that's smart to do, I plan on using Illusion spells for stealth.

I'd probably go heavy on Health. A stealthy character tends to move about slowly and if you aren't attacking with magic then you probably have plenty of time to regenerate your magicka between uses. Raise Stamina as needed.