You can take GMAT during the summer break after you finish all your classes. At the same time, see if you can find some RA for accounting/finance professors at your current school. You won't get substantial reserach experience but possibly something on your vitae/a good recommendation letter/some extra money. In the coming fall see if you can take some accounting/finance research seminar (I am not sure whether you will be allowed to do so). Another alternative is to take PhD level micro and econometrics and get good grades, which will enhance your credentials a lot.
Two possible alternative while you are applying for PhD. 1) Apply for Master of Econ (Yale, Duke, etc..) Of course you need financial support from somewhere. 2) Get a job. Not sure how easy it is nowerdays, but if you are in a decent school and location, you should be fine.