If I take Mirapex for restless leg syndrome and have just discovered it's linked to compulsive gambling, which I have slowly developed over the years, can I pursue a case?

My suggestion would be to do some research and see if there are any class action lawsuits associated with this drug and the possible connection to compulsive gambling.  You certainly can pursue a case on your own, but proving that the drug is solely responsible for a compulsive gambling issue would be very difficult to prove and pursuing a case such as this on your own would be extremely costly and time consuming.  Good luck to you.