Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Under what system are you buying gems? or on what website?
If you haven't paid for them (you said 'I dont have that much in my account', so... you haven't paid for them yet, I would guess) ... then you should be able to un-do the selection of 200.
Let me know a little more, about the context of the selection, and the impending purchase, and I will instruct you.