Most effective websites for advertising cars?

[Christian 1]

Hi, Me again, back with another noobish, exploratory question.

Just want to know what your experience is with advertising platforms out there such as Autotrader and Gumtree. I've always stuck to advertising in 3 places - Gumtree, UsedcarsNI and Facebook, UsedcarsNI being the big one in Northern Ireland where I'm based. Tonight I decided to advertise 2 of my cars on Autotrader just to test the water there. I know it statistically has the largest audience but is it the most effective? Where do you guys advertise your cars and where do you draw the line in advertising expenditure? I have a trade account with UsedCarsNI and would love to have accounts with Autotrader and Gumtree but my monthly bill would be astronomical!