I agree, deeper grow beds! Usually, you want to shoot for around a foot, but my 10 gallon tank was on a 10" deep grow bed (not a big difference anywho).

If you are growing herbs you want lights with more blue spectrum. Try the daylight bulbs from 5500K - 6500K. I found that the cheap T12 bulbs for $1 @ 4100K did great as well. Basically, the bulbs that aren't yellow or daylight have more blue, which herbs can make use of more. Hope that helps