It feels like every time I read a story set in ancient China, the MC is a noble. I think a commoner MC would be a lot more interesting. The only one I have read with a commoner MC is Fields of Gold (which I dropped for various reasons). Interacting with nobles is fine, just looking for a commoner MC.
Here are a few I can think of: Picking Up a General to Plow the Fields it was dropped by the translator for awhile so I put it on hold but from what I remember she is a commoner and works to improve her family by modern farming techniques/knowledge. Btw, it looks like it's been picked up again with regular updates Assassin Farmer she has no memory of who the original was so she makes a commoner life with an assassin she saved. The General's Little Peasant Wife this one I'm not sure about, she was supposed to be a commoner but it got convoluted and I stopped reading it before the male lead showed uo.
You might want to think about what you're actually looking for. Terms like noble and commoner exist in Chinese but they don't quite mean the same thing that it'd mean in Europe for example. Historically, anyone who is not a government official is technically a commoner. So you can be the richest merchant in the whole country, with tons of power and followers/employees and you'd still be a commoner (and a low status one at that). At the same time, even high ranking government officials wouldn't be considered nobility unless they were granted a noble title. These titles tended to be extremely rare in later dynasties. Unless you're reading only Romance novels, I'd say about 80% of historical Chinese novels will have non-noble protagonists. They may not stay that way but it's extremely common to start like that.
You can try these:- Abandoned Peasant Woman: Farming With a Cute Baby Farmer Lady of Fortune, Imperial Concubine, Don’t Be Too Sweet Wang Family’s Peasant Woman: Raising kids and Making wealth Take Taobao to the Ancient Times
Let's see, for JPN ones: Saionkoku Monogatari (named as Colorcloud Palace in anime. FMC's father a palace official (a librarian if not mistaken), she was hired as a lady in waiting for the palace harem) Kusuriya no Hitorigoto (FMC's a resident of the capital red district, got kidnapped & sold as palace's maid in the harem) For CHN ones (I didn't follow them, but I know the story by their description): Your Majesty Please Calm Down The Eunuch is Pregnant The Deer & The Cauldron (it's Jin Yong's work & probably been turned into TV drama several times) Mangas & animes: Fushigi Yuugi Tekken Chinmi Cooking Master Boy
I have never read a novel where a rich merchant is considered on the same level as a noble. I don't get what you are trying to get at, but there was definitely a commoner/noble divide in ancient China. And you didn't have to be a government official to not be a commoner. Besides that, where did I ask for this 'explanation'. Plenty of people understood what I am asking and gave me recommendations.
The Prestigious Family’s Young lady and the Farmer The MC transmigrated into a noble lady that was schemed against by her sister and got sold off to slave traders so her noble status is now invalid. ML sounds like an honest and sweet guy. Not much chapters yet but I'm loving the grounded outlook of the novel so far. It's set in the same universe as Counterattack of the Cannon Fodder Chambermaid, which now that I think about it fits the requirements to a tee (commoner MC in Ancient China). The Little First Grand Secretary in My House Wife is in charge of business and money making schemes to raise her husband into a plump scholar. Husband is in charge of pampering his wife and studying for the imperial exams to dive back to the treacherous waters of politics. I have a soft spot for Romance(?) novels in the perspective of the Male Lead. I read this on MTLnovel since the translator group that brought this to my attention is dead. Definitely recommend Kusuriya no Hitorigoto. I love the MC's unique perspective about how the Red light District and the Imperial Harem works much the same way.
Try Fool's Gold, not exactly during the times before China's unification, but there are still royalty involved.