Do you have your story planned yet?
After you do, you can start by looking for some chipsets, to play around with map making and eventing (since Rm2k3 have no scripting language T_T).
Later, since you are new to game making, you should get some pre-made stuff in other development forums, like custom Menu system and battle system. It will give your game a pro look, and it will be closer to the original Nintendo games (closer != equal).
Guess that's the basics for noob-game-making ^^
If you need any additional help, feel free to reply or PM me.
No more,
~Azura.