To properly answer this needs a building inspection, but here are some ideas.
Cable, jacks, wall plates, patch panels, keystone jacks, cable trays, cable conduit, anchor bolts for trays and conduit, wall plate brackets, cabinets for patch panels and switching equipment, switching equipment (switches routers etc), tools for making holes in walls for cables and wall plates, cabling tools, tools for making holes inside cavity areas, tools for feeding cable through cavity areas, patch cables for the panels and the PCs etc, people to do things.
The number of sockets per office will vary on the office layout and its use. As a basic rule I work out how many sockets are needed for the current PCs and network devices and then double that, and make sure that you have that many available for use from anywhere in the office. My basic is a double socket on either side of each office. Yes this is overkill, but when someone decides to rearrange the office you want to be able to just switch at the patch panel not have cables lying everywhere. And dont forget to check that you have enough electrical power points in each office and that the circuit breakers can handle the load. If you need to put in more power points best to do it whilst cabling.
Always put the patch panels and switches where you can lock them up and keep an eye on them. In a small office you can usually get away with having one large patch panel somewhere very near to your location. If spread over two or more floors or different ends of a larger building set up secure patch panels for each floor/area and run a high speed link between them. make sure everything is properly labelled with unique and easy to follow codes.
Check what the walls are made out ofand filled with.
Spend more time on the dvance planning and you will save time in the installation.