1. Buyers can be sellers and vice versa. So you should start by your closest friends, family and ask to sell stuff there and link it in social media groups for example where there are people interested in buying something specific.

2. You're already using CoinGate to process your payments, I don't really think you need anything else.

3. It's already too many, stick to what you already have.

4. You could make a press release and make announcements in forums like here.

5. Avoid this "verified product" thing, it kills every credibility the website has. We all know that these methods of making thousands per day are fake and leads nowhere.