Hi Lakshminarayanan,
I am wondering whether you want to purchase storage for team site or One Drive for Business. I wonder this because if it’s ODB, each user in SharePoint Online for Office 365 can get an individual storage allocation of 1 TB for personal site content, and the Storage base per tenant will be smaller (10 GB + 500 MB per subscribed user + additional storage purchased).
But you can add storage space to your subscription as this article mentioned: Change storage space for your subscriptionhttps://support.office.com/en-us/article/Change-storage-space-for-your-subscription-96ea3533-de64-4b01-839a-c560875a662c.
If anything is unclear, please feel free to let me know. I am glad to help you.
Regards,
April