Hello mokshich,
I believe that the idea of your project can create a great boost on your audience's engagement, firstly I'd like to tell you a bit about myself.
I've got a diploma on the Signature Track on the course "Gamification" by Prof. Kevin Werbach from the University of Pennsylvania. Besides that, I'm a Lvl 1 Certified Gamification System Designer by the Engagement Alliance. (If you require, I can send you the links to verify this information), and I'm working on the final project of the Lvl 2 Certification as we speak.
As for working in the area, I've developed a system for a start-up company. And even though is still not a public project, we've got already 2,500+ users (and a few interested investors). Right now, I'm working on a system for a small clothes shop and a few other projects.
The first thing I'd like to ask you, is what's the intrinsic value that your project/site will aim to trigger in the users?
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For the bid and completion time. I'm estimating that we might need a bit more time, depending on how clear/advanced the system is already. Anyhow, the price will remain fixed (unless we take more than a month or so, which I think is not likely).
Let me know when to start and how should we interact!