Panda Dome Free AV is a decent option, but it's always good to use it in combination with other security measures. For complete ransomware protection, consider adding tools like Bitdefender Anti-Ransomware or Avast Free Ransomware Decryption Tools.
No need for the paid version IMO. Of course you can alter even more settings in the paid version, but the preset should be fine. They update the app on a regular basis, and it is stronger than many AV modules; plus it offers rollback. Bundle it with any AV of your choice, and you get even better protection.
And yes, I second the vote for AppCheck.