Online classified ads site - duplicate content?

[advertisingcloud]

Hello, I was reading hobo s post on duplicate content. Our web is in the classified advertisement industry and our site is built up like this

Homepage (last 200 ads)  category 1(has the name we want to rank our homepage and around 350 ads) category 2 (around 100 ads)  category 3 (around 60 ads)

Now our homepage has 200 ads that also appear mostly in category 1 but also in others. We are ranking our homepage as 11 th now on Google.

I'm worried a bit that the 200 ads on the homepage are not unique, because they will appear in one other category. Is this OK? Is this duplication? Should we do something? Issue is that we at first started ranking our homepage where all ads were, now there are too many so we show 200 latest on homepage and then they are split into category pages.

[advertisingcloud]

My idea was to either put a canonical to the categories for homepage (so the category 1 would have a canonical to homepage) or to move all of the category one ads to homepage (speed would suffer) and remove category 1 at all.