How do I advertise for free?

[Abel Cig]

Other than GumTree, you should diversify your advertisement place i.e. post free ads to:-
Biggest Classifieds,
Best Online Classifieds,
Craigslist,
Free Ads Tv,
Free Ads Uk,
Free Classifieds Directory,
Free Community Classifieds,
Largest Classifieds,
etc.

Note: Find the right category and post free ads there.
I also recommend you use different advertisement description content so that your posting would not be regarded as spam. Create fresh content description for every free ads posting while maintaining same ads title.

Additionally, use the following avenues for more publicity:-
Social network sites,
Video Sites,
Forum,
Blog,
Press Release,
Article Ssites,
Link Exchange,

It works for me and I believe the same to you and for any advertisers.