In Platinum, you can now visit the secret part of the Wayward Cave, which contains Gible. Yeah, that means you can get yourself a Gible pretty early on in the game without any trouble (well, catching it is a little bothersome). You can also get TM26 Earthquake down there, which is amazing for early on in the game. This video also shows the normal part of the Wayward Cave, popping by the Old Chateau (I go and catch Rotom later on, don't worry), and then exploring Hearthome City.