Three things look for. Never too young, never too much money, never too much memory. Old now, spent money on iPhone, but still have plenty of memory. View attachment 871633
I have 200GB available of 256GB on my iPhone 11 Pro.
I like keeping 25GB at minimum available for futureproofing and updatability. Updatability is being able to update the software without deleting any files like apps, games, and recent photos (my photos are in iCloud).