T13 is a complex series of interlocking systems that can be daunting to learn and use. So there is only one real way to learn, someone has to read the rules and try and understand them. However, you don’t all have to read all the rules at the start.
To begin learning the game you can begin very simply, with Extra / Lite Characters, simplified Lite Annexes, simple Geometry (ignore everything but the main Number which is the easiest one to calculate), a Persona and a Core, 1 simple and specific Hitch, and Value or Dice Tests, maybe play a game set in a simple, primitive setting, literally a wandering tribe of hunters, the group is initially just the players. Initially the Referee will make the Plots small and simple, often creating Geo-Plots for simplicities sake. Over time the tribe grows, and so the Ref adds more rules, perhaps such as Sway, Stress, Tension and Drama.
Over play the simple, probably historical setting may add hints of fantasy, horror, or science-fiction, if the tribe encounters, dinosaurs, lizard-folk, or aliens perhaps in their wanders. Then again the setting may be revealed to be post-apocalyptic, or entirely fantastic early on as the two suns or shattered moons first rise on their adventures. It is even possible that the tribe may just wander from their usual route and encounter a modern city. All of that is up to the Referee or setting Author.
Eventually the Players might grow bored of their Lite Characters, who seem weighed down with simple Hitches, so they start thinking about starting a new one… Instead of creating a new Character, an Archetype or Detailed Character sheet of that Lite Character is almost a new game (Archetypes are a slightly simplified Character that are more similar to familiar systems such as TSRs famous publication). More complex Plots based on Yarn Spreads and larger Facet Conflicts that spread over several Episodes or sessions should be used to increase the entertainment for the players. Or Character Arcs and Compositions could add a deeper roleplaying experience.
Suddenly they can see new ways they could change the Character they have. To combine the Proficiencies they have in complicated ways, to fill Skill, Talent and perhaps Power slots that the Lite version hadn’t unlocked. They have more complex Hitches that vary in effect more than the Lite, and their Talents and Powers are less generic, and probably more powerful than they thought.
Sooner or later your Characters are all Grunts, each with detailed Character sheets, with full Geometries and I-Chings, they have a number of Descendants that they have constructed, but they are getting bored of the setting. By this time you have added Card Tests and Ordeals, mostly for the speed and narrative complexity of Ordeals, and should be using multiple Plots of different sizes at once. With at least one Volume Plot governing the overall Narrative.
If the setting has become stale, then it is time to shake the setting up. T13 has numerous ways you can do this, perhaps your Tribe of nomads are offered a life in a settlement, or maybe suddenly dragons erupt across the world, or aliens invade, or perhaps the tribe’s Shaman actually opens that portal to the Spirit World that the frog told him about. The world and setting can change suddenly, but it can also change gradually. Perhaps you retire those characters and create new ones born a thousand years later, in the city that their ancestors first founded.
At some moment in the game one of the “new” Characters will need a Proficiency or Annex from one of their old Characters. In that moment, make them a Hero (if you can), suddenly they will gain access to Chi and Wyrd Tarot. This changes the nature of the game immensely, as the Characters can bend and warp reality in new and direct ways. By this time the leading Plot should either be an Epic or even a Cycle. After this point in T13 Games multiversality (either directly or via time-travel) usually becomes a common component. When Universes are only separated by the number of “What-If?” questions then it becomes easy to ask, “What if this Character was born in a Fantasy world, and became an elemental-mage?” or “What if this Character was given a super-soldier serum when they joined the army?”. Often in T13 games these alternates are revealed because only 1 Character passes through the portal to the new world, everyone else will play Characeters from that new world.
Eventually after several universes or epochs, with several Characters in one Character effectively, they will Coalesce (or Solo) and become a Yarn-Teller. This changes the game yet again as the Characters can directly narrate their own narratives, using Yarn Cards and Spreads, and each must learn to manage Plots, and Conflicts. Individual Characters should consider having at least one Volume or Epic that they are running for the other Players.
Next time you start playing you can all begin as Yarn-Tellers, Heroes or Grunts as you like. Or perhaps someone will play an Eelafin, Toon, Dæmon or Bulmäs Character, adding more diverse rules and more complexity to the Setting.