I agree with you about to use Duolingo. It's a very good app for learning languages, and you can learn catalan through it. Also, you can watch tv series in Catalan, for example Plats bruts or Merlí (these are good series;)) and listen catalan music when at the same time you read the song (Els Pets or Manel use good catalan)
I found this app to learn new words in Catalan: https://itunes.apple.com/es/app/utalk-catalan/id322411078?mt=8
I hope it's helpful!
I always recommend parla.cat
It's an integrated course with grammar, listening exercises, vocabulary... The progress is slow but consistent, and I found it quite entertaining. And it's free, of course!
To check verb conjugations, you can use this dictionary http://www.diccionari.cat/ You can see the conjugatio chart for every verb you look up if you press "conjugació" :)