Step 1) Cut the MMO out of RPG. Forget especially about the "massively" part until you get filthy rich or you have gathered many years of expierience in managing large game projects and have access to a large team. Put the Multiplayer part aside for now too.
Step 2) Think about what you would like to become, jobwise and/or in this game project. If becoming a programer is your target, put aside the RPG part and Unity for now too and learn to program small games from scratch. If for nothing else than to really know what is going on under the hood of the game engine you will use again later on. Or maybe you will be one of the guys that will write his own 3D engine, for one reason or another, who knows?
Step 3) build you skills to a level that gives you the ability to come up with a cool demo or prototype. IMO, Learn the basics, then quickly move to an existing 3D Engine (IF you still rather want to build a 3D Game than building an engine) and start creating small games and prototypes there. Get some expierience, and create some cool little things on the way.
Step 4) If you still want to build your dream game: Plan ahead. Be brutally honest with yourself, use the knowledge you gained over the last few months and years of learning, and CUT YOUR GAME DOWN TO SIZE! The MMO part has been thrown out long ago, now try to reduce both the core features and the graphics to a manageable level! You need to be aware:
- it is incredibly hard to find motivated, skilled people working for free.
- it is incredibly hard to manage a team, and it will cost you a good amount of your time if you try
- outsourcing to freelancers is a better idea, but will cost you something
Make sure you are aware how much you want to spend: have 1'000'000$? You still cannot build the next skyrim, but maybe a very small portion of that game in the same quality, or something a tenth as big in a much lower quality. Have 100'000$? Now you need to become clever how you spend that money. You will have to cut down game logic, graphics, and the whole scale to fit you budget. Have 10'000$? Yeah, that might buy you a single character from Skyrim, depending on the details and animations... or 10 lower quality assets.
If you have no money to spend, prepare to be very much on your own. Now you need to become both clever about how you tackle things (procedural generation, put details where they are needed and omit them everywhere else), and lower your expectations on scale and quality.
IF your vision is as big as you think, and you produce some good demos and prototypes while learning, you might have a chance to find volunteers.... just be aware they are still a two-sided coin: they might do some work for you, and fill some gaps, but you will need to invest some time yourself to manage them, keep them interestet and motivated.
Step 5) Start building your dream game, step by step. Break it down into the basic components, and build each one on its own.
- A very small test area. Play around with level design, see what works for you wand what does not, maybe start thinking about where you can cut costs by procedural generation, re-use and so on.
- A player character: If you do not have a model yet, use a proxy. Get the player character moving around
- Enemies: as above
- A fight system...
And so on. In the end, you will have a very small scale single player RPG without much story. Now, IF YOU HAVEN'T HAD ENOUGH, and still want to go on, get your fet wet in implementing networking and creating a multiplayer expierience, or expand the RPG with more levels and a story.
And maybe, one day, in some years, you got to release your very own RPG. IT won't by Skyrim, it won't be WOW, and most probably you will have to work hard to match even Minecraft... but its your own baby.