The combat system: if your gnome is in the same space as an enemy gnome, you can play an attack action as one of your action cards. Provided the attacker's combat strength is higher, the defender's piece is removed, otherwise the attack action cannot be performed (perhaps the fact that there are no "unsuccessful" attacks is strengthens the "not a real combat system" hypothesis). Apart from a few boring (and usually known to all parties) bonuses, combat strength is very simple: it's the number of played action cards in front of each player. That might be zero, at the start of a player's loop, or ten, towards the end. Unlike in Olympus, in Gnome, players have some control over when their loop starts and ends.
The question of "value" is an interesting one. I haven't worked it out in Gnome yet - the fact that upgraded actions are not better useful than basic actions surprised me. You mention branching: one of my priorities with the action loops is to create something with all the advantages I've described but without causing players to have only one sensible course of action. The mechanics punish players for backing out of one course of action and committing to another after the loop has started. Sometimes, however, the best start to a loop is one which, though weak, will lead to two possible branches later on. This would lead to a flexible strategy which can respond to opponent's choices.