Well, an 8x10 enlarger and a room to put it in (based on your profile) ...
However, you have really not given us enough information. What format? 8x10? Types of film and paper do you wish to use? Where are you? (makes a difference)
Even so, this is not really something that can be answered adequately in a a forum response (In my opinion) Start by reading some of the basics:
Darkroom design for beginners
Making Your First Black and White Print
Ask some more specific questions and we'll try to help.