Fighting styles determine stats
The first misconception everyone has is the blanket answer, "Oh, you're a beggar, so you want X stats." This is fundamentally wrong. In fact, your choice of primary martial styles determines what stats you will want, and eventually what meridians you will want.
Martial arts are divided into three attributes: Yin, Yang, and Tai Chi. These are further subdivided into external styles and internal styles. Each school has a primary attribute, and this determines which martial arts are effective for that school. For instance, Beggars are Yang attribute, while Scholars are Yin attribute.
Tai Chi users can use all attributes competently (they get a 16% bonus to non-Tai Chi styles and a 20% bonus to Tai Chi). Yin users can use Yin and Soft styles as well as Tai Chi styles, and Yang users can use Yang, Hard, and Tai Chi styles. If you're a beggar, it means you cannot effectively use Yin styles, and you cannot effectively use Yang styles as a scholar. The 20% damage penalty makes off-styles generally undesirable, though some styles are useful for utility even though they deal less damage.
Choosing internal versus external is frequently a matter of preference. Some schools are pigeon-holed into a particular role; for instance, Tangmen are stuck as yin external and really can't use internal styles well. Wanderers are tai chi internal and can't really build for external martial arts. You must choose to go either internal or external; spreading stats is generally a bad idea, and it will become a much worse idea when meridians are launched in April. Don't try to go hybrid; it will not work in the long term.
Below is a list of which styles fall into which groups. Find your favorite style in the list to find out which group you belong to. This is not a completely exhaustive list; there are a number of Jianghu styles I don't know the details of (the PV/LMI sets, for instance).
Yin Internal: Breeze Sword, Rosy Cloud Stab, Golden Diamond Soft Palm, Boundless Sword, Leisure Kick, Green Cloud Palm, Flying Snow Palm
Yin External: Departing Sting, Falling Flower Sword, Golden Snake Sting, Vertigo Dart, Shadow Chasing Sting, Perish Blade, Demon Soul-Chasing Blade
Yang Internal: Lotus Palm, Eagle Claw, Wind-Chasing Blade, Bone Corrosion Palm, Setting Sun Sword
Yang External: Long Boxing, Bodhidharma Stick, Weituo Stick, Crying Stick, Spirit Snake Stick, Soul Chasing Claw, Soul Losing Blade, Mantis Fist, Soul-Stealing Sting of Intrigue
Tai Chi External: Taiji Sword, Yin Yang Sword, Demon Heart Chain Hand
Note that Wanderers can currently pick from both internal lists (they shouldn't learn external styles), and the Tai Chi external list is available to all external martial artists. Also it's important to note that most schools have both internal and external styles, while you'll want to choose only one or the other. As an example, Falling Flower Sword is external, while Leisure Kick is internal. This means that generally, scholars must choose which style they want to focus on and can't really be good at both in the long run. They'll want to pick up other styles that fit, such as Breeze Sword for internal scholars or Departing Sting for external scholars.
Can we talk about stats now?
Most of the conversations I have with people about stats revolve around explaining to people that they can't focus on both Lotus Palm and Spirit Snake Stick at the same time, so the rest is relatively straightforward.
First, damage stats are generally bad. If you're a Royal Guard and you thought your best bet was to stack brawn, think again. Brawn and Breath give terrible returns on damage. The best scalar in the game is Slow Green Shadow (1.5), meaning that 100 breath will give 150 damage to Green Shadow, which is pretty good. Unfortunately, the best normal attack scalars in the game are around .32, which gives you 32 damage per attack (not per hit) for 100 stat points. Those same stat points will give you 700 HP if you invested them in stamina. Most fights are over in under 10 attacks and definitely under 20, making stamina almost always a better deal. Many attacks have scalars that are as low as .9. As a general rule, don't bother with damage stats.
Accuracy is the most important thing to raise. Dodging sucks and a dodged combo starter or linker leads to a ton of lost damage. A dodged Loathsome Clouds and Rain gives your opponent the chance to retaliate with a combo of his own, too. Don't skimp on accuracy! Accuracy is raised by Dexterity/Posture/Balance (the same stat, translated differently) for external styles, while it's raised by Spirit for internal styles. Your mantra should be to pump one of these two stats to its maximum ASAP.
Critical rate for non-Tangmen is a mediocre bonus as the amount of crit you get per stat point is awful. Since crit rate for internal skills scales to Spirit, internal martial artists kill two birds with one stone by pumping Spirit. External martial artists must spread into Brawn. While Brawn does raise HP, it's not that big a deal and should be a low priority.
Stamina is really good, as mentioned above. The returns on stamina are generally much better than damage stats in a real fight. Even characters with low stamina caps (such as Wanderers) will want every little bit they can get.
Dexterity is useful for dodge rate, even for internal martial artists. While it's not a big priority for internal users, a lucky dodge can win a fight for you. Anyone capped on Stamina who wants more survivability can squeeze out a bit more through dodge rating. This is especially important for wanderers, who are incredibly squishy.
Some school internals give special benefits for certain stats.
Reaching the limit
Wudang's Inner Pill Skill has a per-hit buff that scales to current IF. Since Breath raises maximum IF, these characters get a large damage benefit from raising Breath. This is the exception to the "Breath sucks" rule.
Tangmen benefit greatly from raising Brawn for more crit rate, due to the unique interactions of their inner 2 passive. The stacking debuff applied by their passive also scales to Dexterity, giving even more incentive to raise it.
Emei's passive shield from Five Talismans Manual can trigger more frequently the longer the Emei lives. All survivability, including dodge rate, is desirable. This means that Emei will want to emphasize Stamina and will also want Dexterity gear, even if they are internally focused.
Every internal skill has a hard cap on how much benefit it can get from gear. This hard cap is expressed in the skill menu, as shown in the screenshot to the left. The first set of numbers represent the base stats provided by the internal skill. These base stats give you a general idea of what the skill is designed to do, and some of your choices can be influenced accordingly. For instance, Departing Sting is a good style for external martial artists with high Breath, since it has good Breath scalars and no Brawn scalars. On the other hand, Perish Blade is a poor choice for external martial artists with poor Brawn, since it scales only to Brawn. This doesn't mean you should spend a lot of stat points on damage stats, but it can influence what alternate styles you pursue.
The second set of stats show your gear caps. The left-most numbers displayed in yellow are the maximums you can attain from gear, and the right-most blue numbers show how much your gear is giving you. One oddity is that stat bonuses from annotation manuals in your book slot are not displayed properly on this screen but still count toward your gear cap. Other bonuses -- including your base stats, food, medicine, and tactic buffs -- do not and can be stacked on top of your gear cap.
A high cap for a particular stat does not mean you want to emphasize it. This is a very common mistake. Use the advice above and focus on accuracy and defense first. If you manage to cap those out, you can then focus on damage stats. Note that raising Brawn does raise maximum HP by a marginal amount, so if you're really focused on not dying (e.g., if you're Emei), you might want to raise Brawn before you raise Breath, even if your damage skills scale to Breath. This is sort of extreme, but it's something to consider.
This post is a bit complex, simply because the gear and stat system in Age of Wushu
is a bit convoluted and hard to understand. Make sure that you're wearing the right gear for your internal skill (Yin users need yin gear, etc.) and don't go over your stat caps.
Age of Wushu is a wonderous place, full of hidden secrets, incredible vistas and fearsome martial arts. Join Patrick as he journeys through China, revealing the many secrets of this ancient land. The Ming Dynasty may be a tumultuous time, but studying The Art of Wushu will give you the techniques you need to prevail.