From a corporate VP/road warrior, still working, but looking over the horizon at FIRE:
Buy a couple of good conservative dark suits. They will last for years. (If you stay away from the doughnuts and other office goodies... ) I prefer Men's Wearhouse; wait for a sale-They do a great job coordinating your wardrobe, tailoring and alterations, and most off all suggesting color and stye combinations for those of use who are sartorially impaired.
You can spend a few bucks at MW and come away with a plan, then implement parts of it a Burlington Coat Factory, JCP, Jos Bank, Nordstrom Rack, etc. to save $ - (you can buy decent dress shirts, chinos, belts, shoes, ties, etc, at the discounters, but stick with good quality tailored suits. A cheap suit looks like a cheap suit. )
IMO, It is hard to beat Jerry Garcia ties. I think one of the ladies here mentioned in another post that she found them irresistable...
Shirts- I really like Lands End pinpoint oxford shirts. I have some that are over 10 years old, I own a couple dozen, , and have them professionally laundered; they have really held up well, always have five in the suitcase, and a dozen at the dry cleaners.
UncleMick has the ultimate budget solution, but I draw the line at used clothes... That being said, I just dropped off a half-dozen good suits and a pile of other lightly-used clothes at Goodwill, so they do get some good quaity merchandise.
Good luck in your new position. Hopefully all the folks in the office will think of you as "that dapper [-]old[/-] new guy"