It depends, are you doing a planted tank? If so you wanted a higher wattage per gallon, otherwise it's going to be too dim unless you're doing only low light plants. But otherwise, it doesn't matter the wattage.
Generally a 10 gallon kit comes with two 15 watt bulbs for the hood, that's good enough for low light plants. It's not so much the wattage you're looking for but for the Kelvins. 6,500 K is the closes to natural light so around there is what you're looking for for planted tanks