Learn to manage your mana better. You should really only be using Shocks and not on CD unless the fight is extremely short. Otherwise, you're basically an auto-attacker. Get mana potions/dark runes/demonic runes. You'll want to get as much intellect, strength, and crit as possible. Intellect opens up for more Shock casts. Strength for base damage. Critical strike (or agility) for big damage.
Builds I would recommend:
Stormstrike/Mana spring totem. Lowers the cost of totems and makes twisting totems easier:
https://classic.wowhead.com/talent-c...051-0510530105
Auto-attack build/support with an instant cast heal/lightning bolt when necessary:
https://classic.wowhead.com/talent-c...-0510530105001
With better gear, and understanding how to not pull threat, this would be the most DPS after hit cap:
https://classic.wowhead.com/talent-c...05202105023051