I've been playing it throughout the holidays and I'm lovin' it. The confusion is only initial, you'll quickly get the hang of it.
Long story short, collect pairs of offerings and fuse them to get more ammo, once you fuse two three-star offerings, you will get one higher tier offering. Fuse base types of offerings with elemental ones and you get new attacks - simple.
Saving and sacrificing is even easier - save for more HP, sacrifice for more attack power. Sigils will become available to you based on the souls you collected, they will give you additional bonses based on your Divine or Dark arm level, meaning the balance between saving and sarificing.
I gotta say, what I like the most are the voiceovers and the story. Clearly a lot of thought went into the lore of the game, some stories are actually pretty touching. The game plays with your emotions and I find that to be really cool.
Be sure to download all the DLC for it - it's free and subtantially expands the game.