As above, you'd be best off using an SSD as your main boot and programs drive. Due to their price per GB, I don't think it will solve your storage problems. You would probably be better off with a 7,200 RPM 2, 3 or 4TB mechanical drive. Or, ideally, a small SSD (you can get away with 64GB if you only have Windows and programs on there) along with a large HDD.
Otherwise, you should look at archiving stuff from your current drive.