I agree with TelTura and Legolis. The market is winding down a bit and it might be a good idea to either liquidate your collection as quickly as possible (and hope for the best in terms of return) or hold on to it for the long run.
My advice: Decide what you want to keep for sentimental reasons and get rid of the rest. Hang on to a couple of cards from movie block to build decks with, if you decide to pick up the game again later.
Ironically, the less balanced and well-designed cards tend to be, the more valuable they tend to be, and vice versa. So, if you are sitting on cards from set 11 and onwards, especially sets 15-18, the more money you will get for them, whereas cards especially from the first six sets hold little value in the secondary market- unless they are the foiled versions -, yet provide the most fun when playing.
I hope this helps.