Go for monthly return and in case if your turnover exceeds 5 crores rupees then go for QRMP scheme means quarterly return.
GST registration is filed at GST portal
Here are the documents required to complete GST Registration:
PAN card. Aadhaar card. Business address proof. Bank account statement and cancelled cheque. Incorporation Certificate or the business registration proof. Digital Signature. Director’s or Promoter’s ID proof, address proof, and photograph. Letter of Authorisation or Board Resolution from Authorised Signatory.