Under 20 lakhs annual turnover.

I am a farmer and I want to do part time business. In which I sell photo frames and gift items. But now I have a startup, so I have to shop for my business only two or three times a year. And maybe if my products are not sold every month, then in such a situation, I take GST because GST is mandatory for selling online merchandise. So my question is that if my product is not sold or man is not purchased in any month, then what is the provision of filling GST for this?