Please only ask your question one time, in one place. Thanks.
The answer to your question depends on may factors. Factors like:
What OS do you intend to use?
How many users/systems will connected to this system?
What do you intend for this server to do (file server, backups, media streaming, game server)?
What components do you already have (if any)?
What is your budget?
Please clarify your needs and we can help you better.