Foreign exchange earning and impact on business process

I run a proprietary technical consultancy in India and come under GST exempted limit. Now I have an opportunity to earn consultancy in foreign currency and even that total value including local earnings will be well under GST exemption limit. I don’t file GST returns nor charge GST to my clients. I regularly file my ITR3 as required. 

Please let me know what all I need to do or follow in terms of GST, Foreign exchange earnings and income tax implications.

I also have the option to opt for billing as an individual rather than a firm.