Tutorial: Creating a core-data Mod (Not a Map, just a Mod :)

Quick Question

Hello I am vary new still to all this, I want to create a mod that makes a few new rafts that can allow more objects on them like walls an platforms and stuff.
What files do I need to copy over to my mods folder? Also I was hoping to make a place to craft it no just in the inventory.

Any help would be great thanks!