Keep it simple.

You already have the right knowledge and interests to help clients make the most of WordPress. You also have exactly the right type of traffic: people looking for WordPress tips and advice. A side panel on every page, drawing attention to your availability as consultant, would result in more work than you could handle.

Don't waste your time on branded merchandise, don't mess with your audience by introducing any sort of pay wall (no matter how reasonable it may seem in your own head), just keep it simple, connect the pieces you already have and stop over-thinking the problem.