Rosetta Stone is useless - pictures of objects without any grammatical or sentence structure with context won't help you...it's basically a dictionary with pictures.

Pimsleur is old school but works for some. If you have two months to invest and can do skype classes 2-3 times a week, find a teacher who is knowledgable with and can effectively teach using TPRS and CI (Teaching Proficiency Through Storytelling and Comprehensible Input).

Here are a couple links to get you started, and this method is head and shoulders better, faster and easier than any other language learning method on the planet - provided the teacher knows what they're doing and you're putting in the time to practice. There are no short-cuts for memorizing vocabulary, so while TPRS will help, keep flash cards for the trickier words that don't sink in right away.

http://sxole.com/video/learn-greek-via-storytelling

https://www.youtube.com/watch?v=s4x11rJ54TQ