I’ve been learning Finnish at the university for a year, and I found these pages helpful:
1) yle.fi - Finnish BBC, easy to say. The most useful category for me is “selkouutiset” - the news for foreigners. You can listen to different podcasts which people read slowly so you can understand practically everything!
2) oneness.vu.lt - an interactive playground with lots of grammar exercises and some other stuff. This thing requires flashplayer so now it doesn’t work properly on mobile iOS or Android devices.
I also improve my Finnish by chatting with foreigners on Tandem and Facebook.
As for books, I’d recommend “Suomen mestari” exercise book - we use it sometimes at the university and this is really handy.
Anyway, good luck! Hope 15 cases in Finnish won’t scare you 😉