As dropbox is an online service, the disk space you can use with dropbox depends on your package.
2 GB for the free package
While installing dropbox, you can choose the disk space
that you need. You have 2GB free, however if you need more space, you can purchase additional space
among the different packages offered by Dropbox.
If you have only text documents and images, free package may be enough.
2 GB can be compared to a small USB stick.