The rules for this game are a bit of a muddle. Specifically, there has been a lot of discussion about whether a player is allowed to activate/claim an action chip or gem using his second card (i.e. first movement card) and then play a third card to continue movement. A few questions were asked in the forums and elicited a response from Rudiger Dorn, but it didn't really clear up the question.
I took a careful look through the rules today after a dissatisfying session last week (that lasted 18 minutes and seemed far too abrupt) and came up with what I think is the intent, and will play the best.
First, from the rules:
A goblin may climb upon another goblin, a magic stone, or an action chip, resting until his next turn. He is also allowed to step on, and pass over, other goblins, magic stones, and action chips. Overtaking a goblin who already has a goblin on his shoulders, is forbidden.
The rules then talk about what happens after a second or third card have been played. The goblin will either be on:
A vacant square. Nothing happens
A magic stone. He takes the stone (max 2 allowed)
Action chips. He turns it over
Individual goblin. Here is where it gets interesting: this is the only situation where it talks about the fact that the player can land on a goblin with his second card, and then is allowd to play a third card to move up a level.
The general rule is that if a goblin lands on a stone, a chip, or another goblin, he must stop and end his turn - that's what it means when it says "resting until his next turn". The apparent exception is when landing on another goblin, he may play a third card to move up a level, as stipulated in the fourth bullet above (however, it's worth noting that the 4th bullet phrasing isn't specifically identified as an exception).
So, based on the fact that generally when a piece ends its move on a non-empty space, its turn is over, I think that the only way for a player to get to play a third card is if the second card ends on either an empty space or another goblin. If the second card ends the goblin on a gem or an action chip, the player may not play a third card. I think this is supported by the wording of the rules, albeit not as clearly as I'd like.