Not sure if you know this already, but orb movements aren't restricted like bejeweled. You can move them side to side, up and down, and diagonally for a few seconds. There's skill involved in matching orbs. You have to be really good a orb manipulation to get at least 5+ combos. Take a look at this guy playing:
It's a much deeper game than it looks. For example, you can't take on higher dungeons with just any monster. You need to build a team around HP/Recovery requirements and skills. As for skills, there are stuff like changing orb colors, delaying enemy attacks, reducing damage, poisoning enemies, etc.