Keeping cost down on such a high graded set haha that's funny.
But in all seriousness it's very tough to do. The main thing is patients. Easier said than done. What you want to do is set a price that you want to spend on the cards. First commons and then the big name cards. Stay at that those prices and no matter what have discipline to stay at that price. It's tough to do but watching auction houses sometime you can find great deals. Where your being very picky with centering and such may be tough to do.
I myself have been building my set for sometime but I have prices on where I want to be on the cards and I refuse to go above that price. It's been slowly coming together but it also helps with blowing money left and right.
So what to do
1. Set prices on commons and stars
2. DON'T GO OVER THOSE PRICES
3. Have fun building your set