In order to install Virtual Box Additions on your newly install Ubuntu virtual machine, you will need to fulfill the following dependencies.
Install dkms and the GNU C Compiler using the following command:
sudo apt-get install dkms gcc
Install the build and header files for Ubuntu using the following command:
sudo apt-get install linux-headers-$(uname -r)
$(uname -r) in the above command just passes your kernel version to apt-get