Charcoal and navy are the preferred color in a conservative men's suit. Never black.
Fit is key. Nothing smacks of inexperience like an ill-fitting, cheap suit.
Suits are a lot like wine. You can get a nice suit for not a lot of money. You can also get a lousy suit for not a lot of money.
My recommendation is to go to Jos A Banks. They have decent sales, good enough tailors and can often rush the tailoring, if need be. The suits are decent there, their shirts are excellent and their ties are fine (enough).
I prefer this as the standard uniform.
Charcoal suit
Light blue shirt (solid, plain point collar)
Solidish maroon tie.
Black shoes (plain)
Black belt
This can be worn in just about any situation. Save the navy suit with white shirt for evening wear.