Does focus increase fire or ice attacks? I remembered it being ice attacks...
Focus increases the effectiveness of every single spell that a mage has, besides skills such as recuperate, meditate and bandage wounds which are vitality based. (If you go into your skills menu, and examine a skill, it will say what skill it is based on)
if I just use my unlimited heroic energy rejuvs will that suit me for a long time and until what level?
Unlimited heroic energy..? What do you mean by unlimited. If you just mean 20 energy regen, that might be enough until maybe level 50-60. Especially with a DPS intensive build, you'll be aiming for close to 100 energy regen as soon as possible. (Unless you use energy boost/sacrifice, then don't need the energy regen lux)
And is firestorm firebolt and fire attune 20/28
20/28? I don't think there's ever a time where skill cap is 28. O.o What you'll be aiming for is maxed bolt, attune and storm. Then putting some points in lure to maximise effectiveness.
should I invest in E shield if I am fire build?
For all builds, e-shield is a nice skill to have. It can be a lifesaver, if you're almost dead, and your skills can't be interrupted while shield is up, which is really helpful.
What off-hand is good? The book or glowing ball thing?
Until level 100, I advice using the grimore book. It gives focus makes all your spells stronger, whereas the orb only adds energy and a little bit more energy regen.
Is fire build best training?
Fire and Ice have their pros and cons. Fire is good because of its DPS and slow cooldown, and ice is good because of its insane burst damage where you can usually 2 hit any mob. Up to you to decide which is better.
and is there another fire skill strike that im missing....?
Fire bolt and fire storm are your main spells. Then there's incinerate for DoT (damage over time), and cloak of fire.