Need help

Cross posted from other groups! Still same person seeking info.

Good evening, for about a month now I’ve been trying to find a casual/comfortable watch. And seiko is one of my go to brands. (I only own one seiko I just catch myself searching through their stuff) and I came across “Grand Seiko”. I’ve only been in the watch game for maybe 6 months. Within the last month or so have been pursuing more watches. I understand Grand Seikos are more of a luxury which is fine. But I just want to know what to look out for. Do I need box and papers? Are their fakes? Or are there any reproduction kind of thing? Idk I just want some more info on them. The photos I’m using , those ones are selling for just under 600-700$ from what I’m seeing on eBay. Are there better sites to use other than eBay? Thanks in advance.