As on date there is no mechanism for purchase of goods without GST for the purpose of export. However, the GST Council holds the power to notify such categories as deemed exports. Retired persons who are unregistered under GST are appointed as retainers to carry out certain accounting functions.
You can sell online without GST only if you sell goods which are exempted. If you sell goods on which GST is applicable, then you has to get GST number to be able to sell online. You has to take GSTIN even if turnover is less than Rs. 20 lakh.