if you are using commercial as your main income, then goods won`t do very much for you. Technically, if you have even 10 population you will make a profit from the goods, but practically goods are best if you are using tax as your main form of income. When using anything other than tax for income, most people will kill off all population but one from their planets to minimize extra costs of food, but the decision as to whether to keep your pop or kill it is yours. If you do keep it, it`s generally not a bad idea to shove some money into consumer goods, just to bump your income up if you have some extra cash to use.