Luck magic is totally possible with Thaumaturgy. They even do it in the novels.
And I'd totally allow Luck Magic as a form of Sponsored Magic.
Dunno about doing it with Evocation, though. It seems too technical, and I'm not sure how well luck manipulation would translate into the standard Evocation effects.
PS: There are some custom Powers you might want to look at on the list. Here, I'll pick them out for you.
CHAOTIC FATE [-0]
Description: For whatever reason, the randomness of your life is much greater than normal. Your personal bell curve is pretty flat.
Skills Affected: All
Effects:
Chaotic Fate. All of your rolls are made with six fudge dice instead of the standard four.
Aura Of Chaos [-1]. All rolls made in your presence are made with six fudge dice instead of the standard four.
ORDERED FATE [-0]
Description: For whatever reason, the randomness of your life is much less than normal. Your personal bell curve is pretty pointy.
Skills Affected: All
Effects:
Ordered Fate. All of your rolls are made with two fudge dice instead of the standard four.
Aura Of Order [-1]. All rolls made in your presence are made with two fudge dice instead of the standard four.
CONTROLLED FATE [-1]
Description: You can control probability to a limited extent, making life more or less predictable through magical power.
Skills Affected: All.
Effects:
Fate Control. Whenever you roll, you may choose to roll any number of fudge dice between two and six.
Aura Of Control [-1]. Whenever someone in your presence rolls, you may choose to have them roll any number of fudge dice between two and six.
PROBABILITY MANIPULATION [-3]
Description: God's dice are loaded in your favour. Your luck is literally supernatural.
Skills Affected: All
Effects:
Weighting The Dice. Whenever anyone in your presence rerolls dice, you may "lock down" one of those dice. Doing so ensures that the result of that die is the same on the reroll as it was on the original roll.
Palming The Cards. Whenever you are involved in an opposed roll, you may cause your opponent to reroll by invoking an aspect.
Fixing The Wheel. You may take a point of sponsor debt instead of spending a Fate Point when invoking an aspect in order to cause a reroll or when making a Declaration that has to do with random chance. Sponsor debt taken this way represents accumulated bad luck, karmic backlash, or the build-up of paradoxes in the structure of reality.
Stacking The Deck [-1]. Whenever anyone in your presence rolls dice, you may cause them to reroll by invoking an aspect.