I upgraded storage, how soon can I again take photos?

When you have accumulated enough free space on your iPhone.

What's the difference between device storage and iCloud storage? - Apple Support

Internal storage cannot be upgraded, though you can buy more room to offload, for File storage, iCloud Photos, and for backups.

Based on the use of iOS 13 (15.5 is current) this might also a 16 GB model, and that’s never not going to need manual storage management.