This as accurate information as you will find for light levels for planted tanks. The link is specifically for a 10 gallon and the numbers work and work really well! I know the guys who developed this and they have years of experience with this.
First you need to decide what you want to grow. Take the light requirements for the neediest plant and go with that light level.
If you go very high light you will want your CO2 stable and steady and never let it run it out! If you do it will lead to massive amount of algae that will be very hard to get back under control.
If you go with a lower light level then you can get away with CO2 levels that fluctuate a little.
Also, for high or very high light you will need to dose just about everything as far as nutrients if you get needy plants. Potassium, magnesium and micros for any light levels. Nitrates, phosphates for high or very high light.
First thing you need to do is get an idea of the plants you want to have. List them here so we can help you get the best lighting for those plants. It will also help us to get you on track for future needs as far as CO2 and nutrients.
PlantGeek.net - Plant Guide
Both sites will help you find plants you might want and tells what their needs are.
BTW, I have seen a 10 gallon done with 80 watts of Compact fluorescents and pressurized CO2 without a trace of algae. The guy who does it has to do a LOT to maintain it but the growth rates are the best I have ever seen.