Buy the one that you can always wear and would like to wear in the formal occasion. Look for classic style and quality. It saves your money. The calculation is like this: If you spend $100 to buy one, but only wear once, it costs you $100 per time. If you spend $1000 to buy one, but wear 20 times, it cost you $50 per time. And $1000 make you shining.

For the groom's suit.
1. Material: >90% wool. Forget about teflon, and the right place for is is kitchen.
2. Color: dark blue (near black) is most classic color. Black is more for funeral.
3. Style: If he is tall and thin, choose 3 button design. If he is short, choose the 2 button design.
For the groom's shoes,
Suggest black color, leather, plain cap-toe design. They are most classic combination.

Really suggest you to go for brand, e.g. Ferragamo, Gucci, etc.