Wizards

[lathspell]

Gandalf did not drive out Sauron from Dol Guldur. He tried to confirm the identity that they guessed him to have: Sauron. He was till that day only known as the Necromancer.
The White Council afterwards drove Sauron away from Mirkwood, or at least that was their plan and they succeeded. But Sauron was ahead of them and already had his escape-route ready and Barad-dur was already made ready by his Nazgûl.

Saruman, at this point, was already beginning to search for the Ring himself. He knew that the Ring fell into Anduin near the Gladden Fields. His servants searched all the area there, and he took to scrolls of old knowledge. He too participated at the attack of Dol Guldur, but only to make sure that Sauron was away from Mirkwood (which was far to near to the Gladden Fields), and to make sure that the White Council would still trust him as their leader, so that he could still hear all they had to tell about things concerning the Rings.

The Wizards, or Istari, were sent to M-e to guide the Free Peoples against Sauron. They were not allowed to use open 'magical' force (or at least in a very small proportion). They had to instruct them and let them fight and withstand Sauron. Gandalf (and maybe Radagast) were the only ones true to their mission, but Gandalf is the only one of whom we know that has returned to Aman.

greetings,
lathspell