Rendering Demo suggestions

Sorry to bother y’all with something so simple but I’m not having much luck on my own. I’m fairly broke but need to render a project in Rhino 5; I was wondering if anyone could point me to a decent render demo.
I downloaded V-Ray but it doesn’t show up as a valid rendering option or in the plugins menu, and Flamingo keeps asking me for a license even though their site seemed to indicate I didn’t need one so I can’t get it to run either. Ease of use and lack of watermarks would be nice but honestly I need whatever I can get.
Thank you.

What you like to render? Interior/Exterior/Product/Jewelry?