15 series in my opinion but I upgraded from a 12

https://support.apple.com/guide/iphone/use-reachability-iph145eba8e9/ios

I use quite a few and am trying out a couple more on a separate page to see if I like them or not

ScreenTime- I monitor my usage and what apps are using the most battery

Calendar- instead of searching for calendar app it’s nice to see the whole calendar at a glance so I know when i need to check the date and day for future events

Clock- I’m just tryin it out right now because in iOS 17.2 we will be receiving a digital clock but it is nice to have the second hand to watch so I can clock in/out of work exactly on time (yes, I’m aware the reg clock app does the same thing but it’s on a smaller scale)

I have multiple others but what fits my needs may not fit yours so check them out, make a separate page and test to see which one would more useful for you.

Other Widgets I use- Reddit, Siri suggestions, YouTube search page, bank accounts, music, battery, sleep tracking, and smart home apps