Clarify actions and definitions
It's unclear what many of the terms mean for a first time user. "Buy", "Sell", "Bid", "Ask". I think it's important to be very clear what these mean to someone who may not be familiar and make it really simple. You don't have to use the same words as the stock market. You can create your own lingo that makes sense based on the prediction market you've created. At least give a video tutorial or an explanation on what each actions does.
It will be really hard to get mainstream adoption if you're using technical terms. Make it super simple for people. It should be intuitive.