Got penalized by Google due to thin content and spammy backlinks

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Francois-Pierre Marcil: All the domains I`m currently working with have had penalties (don`t worry about this). The past doesn`t matter if you`ve recovered. Those back links scores are very high, do write new content but only if you are sure that all of your current content is good!
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  Usman Ghani: I am still not happy with current contents, so as soon as I will add one new article, I will remove the old one. In this way in a month or 2, i will have all new high-quality contents
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  Usman Ghani: but before this, i am planning to change from HTTP to https
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  Francois-Pierre Marcil: Usman Ghani If you are not happy with the current content, update that (in the existing URL) instead of adding a new URL.
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  George G.: DA is a fake metric not used by google. It means nothing.
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  Francois-Pierre Marcil: I would still claim that it is useful for a SEO to know these metrics regardless of what Google uses. Now, it doesn`t mean one should pay for activities aimed at boosting DA ;)
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  Michael Martinez: When you say you received a Google penalty, does that mean you received a manual action notice in Google Search Console? Because if not, you may have harmed your site`s relationship with Google by unnecessarily disavowing links, especially if you didn`t create the links or pay someone to build them for you.
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  Usman Ghani: No, I didn’t receive any notice. But each of article was only contains image with 100 or 200 words (simple thin content) + I was using link exchange and site wide links + I bought links so I know that my traffic goes down suddenly from the day google implemented panda or penguin
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  Usman Ghani: Michael Martinez do you still think, I should invest on this domain ?
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  Michael Martinez: Well, I think you first need to decide what kind of Website you want. If you start over with another domain, will you just do the same stuff over again? Setting aside what is and isn`t "spammy" or "acceptable" SEO practice, if you don`t believe in what you`re doing then you`ll just abandon ship at the first sign of trouble. Website traffic grows and diminishes over time. That`s natural. Maybe it`s because you bought links and maybe not. Maybe 100-200 words per article is fine. Maybe not. There is no formula that is reliable enough for everyone to follow. What works well, in my experience, is creating the kind of site I would want to visit and link to. That takes great faith in what you are doing.