Believe it or not , Home Depot is a good source. I have bought ECOSMART CFL bulbs ... Daylight 5000k box of 4 costs $15 dollars. Soft white are 2700k around 10 bucks for 4.
These are very bright , well made bulbs.
Lumens are 1600 per 100w bulb
This is a great starting point to get you growing .
Below is a HOOD type light system I built using 8 bulbs running 5000k ( 2 bulbs in a Y splitter per socket. Perfect for at least 4 plants. ( each receive 2 bulbs per plant) . These use only 23w per bulb so it won't kill your light bill. When flowering switch to the 2700k and you are golden.