i swear, over 50 games, always got over 10 kills each game, it's so easy, make sure that if you max e first it'll be a melee enemy against you (akali, katarina, etc), your e does CRAZY amount of damage, almost 1/3 of the opponent health at level 5 with a close W, drop to half with w, sense you'll max it second it won't make much damage.
if you are going against a range champ which like to stay far away (syndra, cassiopia, lux, etc) make sure you max w, sense you won't be close enough to land the full damage of your e,don't worry, W make tons of damage as well.
don't worry about the mana, if you'rerunning low, the enemy should be low as well, meaning it'll be easy kill with 1 good E+W combo.
well enjoy your mid AP OP Taric, and good luck on the fields of justice :D