How do I get my photos on my phone without any duplicates

I wonder if somebody could help me please, I'm about to get a new phone and want to get all of the photos from my old iPhone 6 to my new phone. I know this might seem like a simple question but I can't work out how to do it. If I sync my phone to my computer then I end up with duplicates of ever photo I've edited.

I've tried connecting my phone and computer (using the lightening cable) but when I do that it copies duplicates of a lot of my photos and adds them to my library rather than just copying the ones I don't have. Also if I've edited a photo on my phone I loose the changes when I import them.

I really want to sort my photos out but don't want to store them iCloud.

Please can somebody help.