Easy for 1 item, very hard for many items.
At my work, we keep about 20 or so ads running all the time, but to be on top of the page means editing the item. Its the only way to bump.
These programs will add pictures, choose cities/catagories, auto repost when removed, etc.
There are tons of freeware ones but they will get your posts removed quickly.
And the good ones are quite a lot of $
sample image of autoposter