Unfortunately, upgrading one account doesn’t apply to your other accounts. The expanded storage space for your Dropbox Business account won’t apply to your personal account.
What happens if my personal account is over quota?
Your Dropbox quota is calculated based on the total contents of your Dropbox, which includes shared folders. A Dropbox account can't sync more than its quota, so a 2 GB account (for example) can't sync more than 2 GB of files, including the space taken up by shared folders. Every member of a shared folder can add and modify the files in the shared folder, so shared folders take up space in each member's account.
Sharing folders without impacting storage
If you'd like to share a folder without impacting the recipient's quota, you can share a link to the folder instead. A shared link allows users to view or download a read-only copy of the folder and its contents.