Buy anything you want from ebay, except 3 things.
Gpu, psu, storage. Stay away from those like the plague.
Just shop everywhere else first, know exactly what the current prices for the exact model new are going for, and be careful of 'shipped from China' as they often end up on a boat, take weeks to arrive and if there's something wrong you are out of luck as the return date starts the day they ship, not the day you receive.
I ordered a case directly from Lian-Li, OEM manufacturer in China. Took 4 months to arrive due to Customs as shipping first went through Singapore. That's customs export China, customs import Singapore, customs export Singapore, customs import US and finally put on a plane in San Francisco. Total time on a boat, 4 weeks. Total time sitting on the docks, 3 months. Perishables and medical take Priority, all else takes a back seat and ships when there is room.