benefit by, benefit from

The expression benefit from means to receive an advantage because of the action or existence of something.

• Aspiring athletes benefit greatly not only from participating in regional competitive events, but also from watching world-class athletes in the Olympics.
• The people of Ontario and Quebec benefit economically from the abundance of hydroelectricity.

Benefit by has a more limited use and refers strictly to an advantage received as the result of a given action.

• Newfoundlanders still debate whether they benefited by joining Confederation in 1949.

Note: For the simple past and the present participle of the verb benefit, the recommended spelling is benefited and benefiting.