You could create a folder, on the root of your SD card.
In this folder you should create more sub-folders for to sort in your pictures.
The gallery will show all the folders as albums.

The email's pictures are the folder Download and the camera's pictures are in DCIM/100MEDIA.

The best way to create the folders and sort in the pictures would be to use a file manager on the phone, like ES File Explorer, free in Play Store.
No need to use your MAC

Harry