Honestly man as long as it’s rated and real equipment shouldn’t be a problem. I don’t go cheap on climbing equipment by any means but if the Kn ratings are there I trust them. Make sure it’s listed and labeled as having passed UIAA and CE standards.
Never buy used climbing equipment, never.
If you ever take a fall on your equipment you’re gonna want to trash quite a bit of it after having done its job and buy again.
when you’ve been climbing for awhile and are doing more skilled and dynamic movements you’ll start to discern what styles of Carabiners work better for you and why.