Hi there,
This is a really big topic
I think a panel could get you started on the path, but it'll take more than a couple of hours to talk about everything that goes into making your own RPG.
There are a few basics, though. The most important part is asking, "What's the game system going to add to our interaction?" That is, I imagine my friends and I sitting around, playing our characters. We can do this freeform (like I've done online for over a decade), with no system, and that works okay. We just say what we do, the other people say how their characters react, and so on. So what is it that a system is going to bring to the table? Because the mechanics you add do just one thing: they change that social interaction with your friends. They bring certain structures to the stories you're going to tell.
Old school RPG mechanics often do one of two things here: they either give you something to master and to use against challenges, or they try to create some kind of probabilistic model to represent "what would really happen." Many more modern mechanics do other stuff: they provide pacing, they give you a story structure, they provide inspiration, they put players in a position to make hard choices...
So you shouldn't feel bound by the old traditions or even video game standards. An RPG doesn't need attributes, skills, spell lists, damage tables, and all that stuff. It can work in completely different ways. But! It's possible that your RPG will benefit from one or more of those things. So you just need to figure out what adding something does and how it interacts with your other rules. Don't do something because you think it's the way to do things; do something because you have a very good answer to the "why".
I've created a couple of system from scratch. These range from one-pagers to my current project,
Anima Prime, which is basically my ode to Final Fantasy, mostly VII and X (it's Creative Commons licensed, so the whole text is available on the site). The idea is to play FF cut scenes, basically, but none of the grind. So all scenes are either character interaction, or they're the kind of fights where the characters lock swords in mid-air, do battle on top of moving trains, or something similarly dramatic. There is no "roll to see if you can jump far enough" -- of course you can! You're Tidus or Cloud or Tifa or Khimari, you don't fail at basic tasks. You're always awesome. The question is, since your opponents are awesome too, who comes out on top? Then there are some rules for making sure you can do all the cool things from those cut scenes, like summoning creatures to help you fight or doing some major power move. But also, there are little rules that make sure that your personality shines through and that the character cut scenes actually matter; if you have an unrequited love, and you played that out in a scene, then you can bring that up again in a fight later and get some bonus for that.
I would suggest checking out some simple systems first, to see what they add. Some examples are
Lady Blackbird,
Ghost/Echo, and
Geiger Counter. Pay attention to how Ghost/Echo doesn't have any stats for characters but lets the players make tough choices after most rolls... and how Geiger Counter invokes horror movies by ramping up the opposition over time and giving characters more dice against it if they've watched a fellow character die.
Again, if you want to create your own RPG, don't start by taking existing rules and thinking "This is what an RPG is." Start from "just freely playing my character with my friends" and see what you want to add to that. Looking at other modern RPGs might give you a bunch more tools that you can use for this stuff.
If anyone wants to create a panel for this, by the way, I'd be happy to sit on it
