Which photo Gallery app is best for this phone, the Teracube. I have the Google Photos but seems to be running out of memory unless I’m utterly confused about. 🤷🤷
My old phone is a LG_G5 and it has a gallery that I loved. No issues with my photos and everything as it doesn’t connect to Google drive or whatever that links to Google.
Any advise on which app to use without using the Google app?
Much Thanks! 
If you are an Amazon Prime member, the Amazon photo app works well and has unlimited storage. You can also use your stored images on other Amazon device, like Fire TV devices.
For Google Photos, if you tie your app with your Google account, you can have the app to sync your photos to the cloud to saves space on your device. And depending on the setting you have on Google Photos, you can save up to 15GB in original format, or unlimited storage if you enable compression (ie. smaller resolution from original picture).
I second @anthony’s suggestion of using “unlimited high quality storage” with Google photos. I have been using it personally for last 8+ years. They might do something to my photos to reduce the size - however they seem fine to me on the phone and on desktop.
Google photos may not work for everyone though. Here are some articles with recommendations:
If you don’t need cloud backup (or any connection to Google), may I recommend the free and open-source Simple Gallery Pro. It’s available on the F-Droid app store (an alternative app store for free and open-source applications). It’s a good, no-nonsense gallery app, that’s also quite customizable.
Don’t forget to make manual backups of your photos, if you forego the cloud backup options.