Best way to keep iPhone photos but remove from phone?

I have about 3 gb of photos in my camera roll and only a gb of space left on my iPhone. I'm going on a trip soon and want to fake pictures wi my iPhone so I there any way I can put my photos on my computer and just get rid if them on my phone so I can take more pictures.

Plug the USB in to a computer and open the file folder for your iPhone. Not iTunes but going into my computer and seeing devices. Create a new folder anywhere on the computer & copy& paste photos from iPhone to the folder. This is using windows. I'm sure you could do the same with an apple computer system.

Save the photos to your computer and delete them on your iPhone.

Use DropBox i believe you get 5GB for free and get to use the app on the phone for easy access of the pics.