Every situation is going to be slightly different in your needs, but generally here are the overall components you will need.
- Gigabit network switch. This will connect all of your LAN devices and give you the network throughput to support transfer and access of data from multiple simultaneous computers to your server. Count the number of network devices that need to be wire connected (don't forget to include things like printers, wireless routers, and server) and then add a few extra for growth. You don't want to purchase a switch with JUST enough switchports for your current needs and then have to purchase a different one a year from now because you want to add another computer and printer. Leave room for expansion.
- Server system. If you already have a rackmount cabinet then you can probably go with a rackmount server but be cautious about size compatibility. Rackmount servers like the HP ProLiant DL320e G8 can require at least 30" of mounting depth for the rack rails, and not all server racks have that much mounting depth. If you don't have a rackmount cabinet already, it might not be worth the additional cost to purchase one at this point unless you are planning to grow to multiple servers, switches, routers, and UPS systems. A pedestal server system is like a standard desktop computer. The ProLiant ML310e G8 is a microATX desktop supporting up to 4 hard drives so it's about the same size as a standard desktop. You will want a keyboard mouse and monitor to initially configure it, but once it is up and running will not need to have those. Some more powerful servers, such as the ML350p G8, are much bigger physically because they accommodate much more hardware.
- Server hardware. Depending upon how you order your server system, it may just be the base configuration, and you may need to purchase additional hardware to fit your needs. This may include additional RAM and your necessary hard drives. Be aware that HP Generation 8 servers requires HP Generation 8 compatible hard drives, which are more expensive than standard hard drives, but are enterprise-class drives with their HP SmartDrive caddy system specifically for these servers. There may also be some additional optional hardware you wish to purchase, including redundant power supplies for your server (if supported) and an add-in hardware RAID controller.
- Server software and licensing. This is the cost of licensing the operating system with whatever OS you choose, whether that is Windows 7/8 or Windows Server 2008/2012. Server 2012 Standard can actually be a pretty substantial portion of your total costs, so do not forget to budget that in if you are working on an overall budget or expense plan. Depending upon which OS you choose there will be different ways the licensing will work. For example, a single license of Windows 8 will license a single computer, which means you'd also need a separate Windows 8 license for each VM also running Windows 8 if you decide to virtualize that way. However, if you go with Server 2012 Standard, the licensing allows you to install on one physical server AND use that license on up to two virtual machines running on that physical server. Additional virtual machines of Server 2012 on that same physical server requires purchasing an additional "add-on" license for Windows Server 2012 Standard.
- UPS battery backup. It is very important to protect your server from electrical fluctuations which can damage computer equipment. You also don't want your computer suddenly powering off in the event of a power outage, which could cause damage to hardware or data on your server. I've known situations where files and databases were corrupted because a computer system shut off from power outage suddenly and damaged the files currently in use. Picking out a UPS can be difficult. You want to be sure to find something that is PFC compatible and at minimum has the rated wattage support as the maximum wattage of the power supply of your servers. Also, be careful how many devices you connect to battery on your UPS as the more you have running on battery the less runtime you will have. Most of the times when discussing this with customers I recommend a 1500VA / 900W UPS for running a server system with 500W power supply or less and connecting the network equipment to the battery backup as well. If the power supply in the server is greater than that, or redundant power supplies are being used, then I'd suggest at least a separate 650VA /300W UPS for running the network equipment separate of the server.