Yasmine,
I've used google promote for select items as well, and have made some sales through google. I think it's a great feature. I just strongly suggest you start off with budgeting only a small amount of money each day, and choose which items you promote wisely.
Google promote offers great features to view how many click throughs you received, how many people purchased an item after clicking a google ad, and what your profit versus fees are. This allow you to make changes to your advertising.
I hope this helps. And fingers crossed that you make some sales with google!