According to the Android security chief you don't need a anti-malware or anti-virus applications on your device.
Applications on Android are sandboxed, so it is much more safe. You don't have to worry about anything if you are installing apps only from the Google Play store and update them. If there are any suspicious apps, people get to notify it and the Play store removes it.
Play store had removed 700,000 malicious Android apps found in Google Play store last year
In most cases when you install an anti-virus or anti-malware, your phone gets another process to run throughout the day consuming your processor, memory and battery.
If you keep away from rooted device, third party applications, fake download links, and phishing websites your device will be safe.
Some anti-virus applications helps you filter out the phishing sites and spam messages, which is great but at the cost of performance and battery life.
Pi-Hole is a good choice. There are some applications for Android devices which block the ads too. What I personally use requires a rooted device and I would not recommend doing that. It filters out most of the adds which pop up while using the applications or while browsing.