umm.. if you can spend the money for a 250 watt hps i would but if you cant the best would be to get some cfls. blue spectrum for veg and red for flowering
a timer should be about 6-10 bucks at any freddys or kmart.
your plants are too far from the light if there strestching so move the light within 2 to 4 inches from the tops of your plants.
im using 1 4foot cfls with only 2 flourecent tubes. one cool whit and one warm white. both of which are 40 watts.
i only have 2 growing in my closet but heres a pic of how there doing with just that.
How about you buy some cfls for now and hopefully you can afford a larger set up later? You can buy four bulbs for about 12-15 bucks and buy some clamp on reflectors for about 12 bucks @ Wal-Mart, that would buy you some time....