I suggest you set up a game design document or at least something like a very detailed roadmap of what has to be done in which way.
What I am missing are the fundamentals of your game like:
What combat system you want to use - tab-targeting or free targeting as well as the corresponding character stats and how the engine respective client - server - combination handle the combat (process it like physical collision or write something on your own like Tera).
The next thing is: what is your game about? PvE or PvP or both? or something completely else?
For PvE you need an AI System, while for PvP you need to balance out the character classes and races.
What brings me to the next point: Balance in general.
You should start out and work out a concept for this balancing since this is a major point. As well as get started with character stats and the functions which handle Damage Calculation, etc.
What I suggest (I am doing it that way) - do a concept game. This game features everything the game has to have without the additional content. IF you got the very basic game engine done you can build everything in it.
But as I said initially - set up a roadmap. Otherwise you lose your view over the project.
If you ask for specific features (idk, AI.Spawn, GUI Implementation, etc.) we can help you more. I mean I am building up a concept game for an MMORPG so maybe we can exchange some code snippets
For reference buy Esenthel RPG and Esenthel MMO. Ineisis is a bit too much for the beginning but also a very good one.
N.V.
Addition:
for a pet system look at the game "Rappelz" It features pets in a very good variety so yeah.
http://rappelz.wikia.com/wiki/Rappelz_Wiki
At this wiki you can find many examples for stats, damage calculation, etc.