I used to be in charge of computer classes for a large metropolitan area for Age UK, and currently volunteer as a computer mentor for a local charity.
I would not pay for Interet Security products, as the freeware (software you can download for free) versions are more than sufficient for home computing needs. For most computer users with a Windows Operating system, I would dowloadig freeware versions of the following:-
Avast antivirus (Best Free Antivrus in a recent Which? survey) - make sure you only have 1 antivirus program installed as 2 or more would drastically slow down your computer. So make sure any other versions are properly uninstalled.
I also use 2 free versions of antimalware programs, Malwarebytes ad Spybot 2. The free versions of these programs have to have the scan option manually requested. I usually run one on the 1st of each month and the other on the 15th of the month. Set an e-mail calendar reminder to remind yourself.
After upgrading the computers of many of my friends, family and class members computers to Windows 10 (there was a free upgrade offer which runs out shortly) I also downloaded another free version of 'Advanced SystemCare 9' which will ensure the user a faster, cleaner and more secure PC by optimizing and fixing all kinds of PC issues.
I always try to recommend solutions which are free to download ad use.