If you want to take humanities, then the choice of your optional subject may depend on many factors. If you want to go for a corporate job in the sectors like finance, consulting etc, then choosing Economics as your optional should be the ideal choice.

If you want to prepare for civil services, then History is considered to be the best due to it's less complex nature and easy availability of coaching for it. The same goes for Home Science or EVS. And rest you can always choose a subject according to your level of interest in it without taking any factors in consideration.

Hope I have answered your question. All the best!