Never buy a pc off ebay. You have no customization, and sometimes you get scammed. you should build your own
Anyways, It depends on what you're going for. If you're using your pc for office/work, then you might want to build your own. You could save money by not buying a graphics card, because those are meant for gaming. It's your choice whether or not you want a graphics card or not. (for example: Would you be playing minecraft? Using photoshop?) If you are aiming towards a "Gaming" Pc, then you should obviously buy a graphics card, if you don't want to be staring at a slideshow when you try and play minecraft. I would recommend using this website called "Pcpartpicker" It's really helpful when it comes to building your own. You should try it
www.pcpartpicker.com
That's the web address, and I hope this information helped
-Hayden