Second hand would get my vote with your budget everytime, however, if you don't have the confidence to buy used, or you have no-one to take with you to check it for you, then the Triban* is the goto bike at that price point.
*at least the original red T3 was, I haven't heard a lot about the latest version TBH. The wheels were the weakpoint of the original bike, but the frame was good enough to justify subtle upgrades over time. Just make sure the hubs are well packed with grease and they should serve you OK until you decide to either upgrade or, (God forbid), you decide you don't like road cycling.