You are correct that apps that claim to clean your phone do not help. All they do is take up more memory, like you have found out. You most likely have seen these advertisements while playing games and they convinced you into installing them by making false claims. It some cases, they just flat out lie to you and tell you that you are running out of space.
For tips on reducing your iCloud storage, look here:
Manage your iCloud storage - Apple Support
For reducing your device storage, first delete all those cleaning apps. The device storage is limited, so you will need to remove the data to make more room. This could be photos, videos, or apps. For photos and videos, you do have the option to use iCloud Photos with Optimized Storage, to free up storage space on your device, but this will increase your iCloud storage and may find that you have to purchase additional iCloud storage space if you are unable to free up enough using the tips above. Use these tips to help with device storage:
How to check the storage on your iPhone and iPad - Apple Support