How many lights do I need for my basement?
11' x 50' is a rather odd shape but lighting it is done like any other space, first and foremost consider what you will be doing and where you will be doing it.  Is it one big entertainment space?  Is it a combination media area (tv on one side) and play area?   Is part of it an office that will need task lighting? Before even considering how many or how bright the fixtures are, imagine yourself using the space.  

One common rule of thumb is 1.5x the square footage in incandescent watts, i.e. if you are lighting up all 550 sq feet you will need about 825 equivalent watts, or 14 60 watt fixtures.  If part of it is just a media area that won't need a great deal of light you can reduce the fixtures in that section and focus on the other areas.

Edit for future-proofing: to consider this in lumens, a living space is best lit with 20 lumens per square foot and LEDs that range from 750-850 lumens per fixture would therefore require 14-15 fixtures to fully light the area.