There are a few ways to apply Rule Two (Save for a Rainy Day) to your wildly fluctuating income situation. This also applies if you happen to receive windfalls, but are otherwise on a fairly steady income.

Your budget will never be perfect, because you're dealing with imperfect variables (people, external events, and bad data).

The key is to give them a taste of how good it feels to save up and pay for something. Positive, achievable, and life-changing.