1). Here is the link to the “Ultimate Tutorial 2”
This will teach you the Buildfiles hacking method, which allows you to add and remove things from your project without fear of breaking the ROM file.
This tutorial really is the gateway from low-level to mid-level hacking.
2). Here is the link to the intro ASM tutorial
ASM (Assembly Code) is a low level programming language that converts into hex very easily (Pokemon Red and Blue were written in ASM). By learning how to write your own ASM code, as well as how to find routines within Fire emblem, you unlock the ability to change just about anything in the game (granted you do everything perfectly).
This will give you the first step to not only to use someone else’s code (combat artes in sacred echoes), but to actually create your own custom mechanics.
3). Head over to the Tutorials topic on Feuniverse
Under the “Tutorials” topic you will find ~85 tutorials written by FEuniverse users over the years on a wide variety of topics. There are tutorials on music creation and insertion, making custom sprites, importing tilesets from other videogames, Eventing, splicing, ASM, and so on.
Many of the tutorials are either outdated or unfinshed, but the ones which are complete can give you the tools you need to hack every aspect of the game.
In short, there are too many tutorials to list them all, but learning the ways of Febuilder, Buildfiles, and Assembly will send you well on your way to high level hacking.
(Also don’t use Feeditor, it will break your ROM)
(for real, you really shouldn’t use it at all)