CCG Mining or Hashflare
I am not an expert in cloud mining but I manage to find you a link that explain in details what you might want to know. https://bitcoinmining-cloud.com
As you have already mentioned, CCG Mining or Hashflare are trusted but I like to add a word of caution => When engaging in any type of cryptocurrency mining there are risks, but profitability is possible if you make the right choices.
A promo code is just a marketing tool to get you involve in the program or plan. Investors should only invest in cloud mining if they are comfortable with these risks - as the saying goes, never invest more than you are willing to lose.
Yes, promo codes are tools for attracting new users. But they still give bonuses or discounts, right? So, if you are ready to invest, it’s stupid to refuse using codes as they increase ROI. Btw, as for CCG vs HashFlare, I know for sure that the second site has bonus programs (they are listed here: http://hashflarecode.com/ ) and what about the first one?