Erm, what was your spec like before?
Ways to boost atr: High Int, which gets you more bang for your buck in your focus skill, a high focus skill, +atr weapons ( meaning you need a decent hammer skill ), precise rune ( +5% atr, not much, but every little bit helps )
As for mana, there's only spirit, and +spi and +mana items. As a fessor i've heard the strat is to have more health items, since you can just Inspire for more mana, but i don't really buy that one. Seem like you could easily get into a situation where you are constantly Inspiring to cast another bolt =P I'd go +mana +int mana regen items.. with some +int +mana +focus skill mana regen rings, you could get your atr up there pretty high..
Personally, I got a bw rune for my mage assassin.. just for dual wield. Spellwise, that lets me hold two +atr weapons, as well as double backstab.. Wednesday's spell atr is 1100ish at level 45 with 130 int ;x
Hope that helps..