Re: ebay......
As long as you exercise care, I would highly recommend Ebay.
I've used it over about 4 years for about 25 purchases and a few sales. I've always got what I ordered in good time, and at a price I was (obviously) willing to pay.
However, be careful. Certain items (e.g laptops) seem to have a higher risk attached - buying or selling.
Browse for a while before buying, and start with some low-value items. Always check feedback - though it's not infallible.
Have a look at the user forum to see whats happening.
Read the ebay guidance.
After a while, you get a feel for who/what's safe and a good or bad deal.