Michael in your price range the usual recommendation is a Guan Sheng (GSO) dobsonian as being by far the best bang for the buck.
The optical quality is right up there and just as good as some of the far more expensive options such as Meade SCT's.
If you use this sites search function youll see many discussions about this scope.
http://www.andrewscom.com.au/site-section-10.htm
The same scope as the Bintel BT- series
https://www.bintelshop.com.au/
What are the pitfalls at looking at second hand stuff i.e EBay etc.
Many !
Unless you really know your stuff you are very likely to spend your money and come away with a scope that dissapoints you.
Ebay is a real minefield when it comes to scopes and theres very few pearls amongst the trash.