Saying 'for sure' would be an odd way to answer the question, unless you were being a bit sarcastic (i.e. as in "of course it's a pretty dress"). Normally, you'd just say "Thank you".

For American English: "For sure" was used a lot in the 70's. (I remember and used it a lot myself!). It was a temporary phrase that didn't last and it is no longer acceptable to use. Also, in spoken language, we don't use the word "smart" in describing inanimate objects that we like. (I think that was another 70's - maybe 80's common phrase?) "Your dress looks great on you!" "Thank you." It is a good idea to accept compliments with a "thank you". That never goes out of style! :)

'Smart' used in this context is outdated. Are you using an older English textbook?