i'm thinking to buy C2 ,and i started of thinking when i tried it for 2 weeks only but i still need to learn more before i buy it also i had some problem in payment in my country as ages and these stuffs... also construct2 is the best program you can find for html5 and there will be some ways to export to android ,iOS soon (they working on it).
about facebook i think there is some people already had games on facebook i never tried but i think facebook use html5 export.
even if you bough construct2 you will get the updates so you can use it in the future when you feel comfortable with it.
good luck ^^