I have developed a free Tagalog Learning app with Audio and its now available in Google Playstore. 

I believe a Tagalog learning mobile app that has audio recorded by native speakers will help you a lot. I hope this app may help you learn Tagalog : Learn Dalubhasa's Easy Tagalog https://play.google.com/store/apps/details?id=com.dalubhasareviewcenter.easytagalog . This app will teach you from different ways of counting in Tagalog, telling time, travel and dining phrases to advanced Tagalog. This app consists of Tagalog words and sentence structures and offline dictionary with example of sentences. It also has detailed explanation even on using affixes, verbs, adjectives, slang, Taglish, and idiomatic expressions.

Being a native Tagalog speaker, I must say that the easiest part could be nouns and adjectives. Verbs, idiomatic expressions, and active and passive voices are the most difficult. Well, it really depends on how people learn. 

I hope this app helps you. Let me know what you think... ;-)