I have 9.5k mana, that gives me more nearly 500 mana for being gnome. It's a fireball, which usually hit for more than 2k.
Spirit? I don't use it that much, altough I do have lots of it in my gear. For evocation. And it's well more than enough. A lot more than enough, actually. I can fill my mana bar with what I have (plus spirit weapons). I have absolutely no need for more spirit.
As for Diplomacy, it is handy, but then again I'll just have to grind a bit more.
Perception, however, has no real use in PvE (which is my game) except for some sporadic, specific mobs. 500 mana from +5% int and another 650 saved from escape artist = 7k damage. For being gnome. It isn't that bad.