Battlemage?
I play as BM, with Destro and Conju as focus (going to max both trees (possibly) minus one or two perks each (rune mastery, something from Conju)). Smithing and Enchanting secondary, as i wear heavy armor. All heavy armor perks from Smithing but not Advanced Armor's one. All but recharge/soul stealer perks from Enchanting as i don't use weapons (other than bound sword occasionally). I probably don't have to spend points in Heavy Armor, Daedric Armor upgraded to Legendary status and enchanted should give me enough protection though Conditioning would be useful as i don't focus on Stamina at all. Any leftover perks will go to One Handed for Bound Sword or artifact swords.
There are no truly useless perks (outside the whole lockpicking tree) though some are rather marginal, catering only to specific playstyle.
Remember that if you use Alchemy or Enchanting, the basic perk needs to be upgraded to max ASAP. Otherwise choose only the perks you really need. From Enchanting, for example, don't pick weapon enchant perks unless you intend to use weapons with those enchants.
Are you going to be a summoner or a necromancer? I'll go both so i take all perks but unless you do the same, you might choose only one path and leave the other alone. I'm not convinced Conju Dual casting is useful, 60 second is good enough spell lenght most the time, at least for me.
In Destruction remember to consider are you going to use all damage types or not. And if you're, do you really need the special effect perks for all? Flame and Frost ones are quite similar in practice, not to mention nigh useless most of the time, dying targets are dead so soon anyway.
Both Alteration and Restoration have useful perks but you probably won't get enough perks to maxime both ones so consider carefully.