how many watts do i need for my 30 gallon tank??

a 1x96w PCF would be v.good
a 2x39w T5-HO would be better
but with this much light you would
need DIY Co2 and to leave it on
for no more than 8 hours per day,
but you could grow anything well.

400W MH pendant....at least that.

No, just kidding. What kind of plants are you looking for? Carpet plants too? CO2?

With just a few plants, 2 watts per gallon is a good ballpark.