Hello Jack,
It sounds as though you're having issues connecting your iPhone to a Wi-Fi network, and issues with apps not connecting to cellular data.
Resetting Network Settings is a great troubleshooting step to help work towards a resolution. In addition to that step did you complete the steps outlined in the following article? If not, complete the steps outlined there
If your iPhone, iPad, or iPod touch won't connect to a Wi-Fi network
Also, let us know if you're having issues connecting to one specific network, or all Wi-Fi networks.
With reference to apps not loading content when connected to your cellular data network, do you notice if this is with all apps or only specific apps? If the issue is related to specific applications have you verified that Cellular data is enabled for those apps in Settings > Cellular? If not, confirm those apps have a green toggle next to the app name. Let us know how that goes.
If you're seeing No Service or Searching in place of your signal bars check out the steps in the article below.
If you see No Service or Searching on your iPhone or iPad
Have a great day!