GST reg required for online selling ecom(casual taxpayer)

Thank you all for reading my query, Kindly help me starting a GST compliant business. I have Query which i find difficult so far to find an answer. I wish to start reselling some taxable product purchased from mumbai vendor and start selling them on online marketplaces like amazon india. E retailers like flipkart amazon etc are asking GSTN TIN TAN etc for registration myself and by business +my principal business location ( bangalore co-rented apartment place with friends) Should i register myself as preopreitor as a new casual taxpayer in gstn.gov.in to get GSTN id ? Or i have to apply as a propreitor for shop establishment act in bangalore and then migrate to GST. Am not sure this online venture would be profitble or not, this is an effort to understand the business so i would not like to invest a lot to get so much documentation etc to register business. the biggest problem of registering a business a renting a place only for registering a business and from home it cant be done due to residential rental agreement. What is my best option in this scenerio to start online business( get a GST number )or being a casual businessman without any permanent business place. Can not i do business? Regards, A casual tax payer