For pour over/filter type, I'd say the Aeropress is a cheap and easy solution. For larger volumes, a Technivorm will do you >1l at a time.
For espresso-based drinks, our office has a Gaggia Classic. Which is great and can be had for £150 2nd hand, but requires a serious maintenance schedule when used heavily (~50 shots/day or more).
It's obviously important not to forget the coffee itself! Grind fresh if at all possible. If not, then get the roaster to grind it for your brew method. Depending on the size of the company, you can set up a weekly/two-weekly delivery so you've always got fresh coffee on hand.