French-born Lyon striker Toko-Ekambi scored two goals in the space of eight minutes at the start of the second half, leading to scenes of ecstatic celebration in Douala.
His goals were just reward for Cameroon, who completely dominated against a Gambian side appearing in their first ever Cup of Nations.
Reaching the quarter-finals was an extraordinary performance for the tiny west African country, while Cameroon march on to a last-four showdown with either Egypt or Morocco as they continue their quest for a sixth continental title.
The host nation's first and only visit to the country's economic capital in the tournament meant there was always going to be a frenzied atmosphere in this chaotic, football-mad city as fans descended on the Japoma Stadium.
The Indomitable Lions had not taken to the field since Monday's tragic crush prior to their last-16 game against the Comoros in Yaounde, a disaster which left eight dead and 38 injured.
