The sentence should be corrected to sound more natural: "This dress is nice, I will take it." The phrase "for me" is unnecessary because "I will take it" already implies that it is for you.

This dress is nice, I will take it for myself. But more natural: This dress is nice, I will take it. You don't need 'for myself' unless you are shopping for other people as well and want to clarify who the dress is for.