IMO Quora started great but now they are trying to do too much.
So, I would just pick up Quora and would start to remove things. After you remove A LOT of stuff, remove more.
I would also try to create a single reply per question (kind of what RapGenius does for lyrics) needed time to think a way to make this work properly but I think there is something interesting that can be done there because most of the time you end up having to read a bunch of answers to get to a conclusion.
But essentially I would remove stuff and would start with a niche.
The first year for me is the year to prototype as much as possible. Do the MVP (minimum viable product) with quality and track down analytics to the user engagement.
Start with the core idea and build out worth. The less features the better. Make the essential and remove all non essencial features.
The goal for the first year is to prove that there is a market/need for your idea. If it doesn't grow on it's own, then probably you need to tweak it and adjust your initial idea.
Users should bring users. Users should come back. If that doesn't happen, then probably you are working on something that can make all the logic in the world but that users don't want or need.
In a nut shell, the first year is trial and error. Analytics, tune up, change, try again, until you reach a consistent growth.
I read about 2 things: drive large traffic and expand to bidding platform.
What you should be doing is the million dollar question: how can I spend $10 to get a sale and profit $20 from it.
Notice: sale, not traffic or user.
Like you mention, there are tons of ways to get traffic but you don't want 15 year olds from India by the million visiting your site. What for, right?
The way I would approach it is via trial and error. What works for your competitor may not even work for you.
But please, never go on all fronts. That never works. Every startup with limited resources that I see create a Facebook Page, build a blog, doing SEO, email marketing and so on, they fail.
I can take a call with you to understand better what resources you have and give you my opinion on picking one channel to try for X amount of time, what to do, what to expect and how to track success.