Ranald is a strange god. Almost all citizens of the Empire worship him when appropriate, the common sign of the crossed fingers being an entreaty to him for good fortune. And yet he is almost as actively suppressed as the Outlawed Gods, such as the elven god of murder, Khaine, or the shipwrecker's god and enemy of Manann, Stromfels. To understand why, you must understand the fourfold nature of Ranald.
Most know Ranald as Ranald the Gamester, God of Gaming, Gambling, and Luck. A prayer to him is a thumb on the scale of chance, tipping the odds in your favour. He is especially venerated by those who make fortunes by chance - gamblers, of course, but also merchants, businessmen and traders. He is worshipped by most citizens in small ways, with crossed fingers, lucky amulets and superstitions all being prayers to the God of Luck. Trade and business guilds are often dedicated to him, and small, hidden shrines to him can be found in most slums and shanties in the towns and cities of the Empire and beyond - except in Marienburg, where a large temple to Ranald stands openly. It is also said that anywhere there is gambling is a shrine to Ranald.
The second most followed aspect of Ranald is that of Ranald the Night Prowler, God of Thieves. Though this aspect is poorly looked upon by most of those in power, the Strictures of Ranald the Night Prowler frown on violence, so cities with a criminal underbelly dominated by Ranald are vastly preferable to those dominated by Khaine. Worship of Ranald is built right into the Thieves Cant, the deliberately confusing argot of the underclasses, and the majority of Ranald's priests began by worshipping this facet of him.
The least-known guise of Ranald is Ranald the Deceiver, God of Irony and Illusion, Charlatans and Tricksters, favoured by spies, liars, con artists, and Grey Wizards. He smiles on attempts to outwit and outfox your enemies, though he smiles just as readily on suitably entertaining failures. To openly admit to worshipping him is to fail at doing so, as no true liar admits to being one, so worship of this guise tends to be more personal and uncodified than even that of Ranald's other followers.
And finally, there is the most thoroughly and enthusiastically suppressed face of Ranald: Ranald the Protector. He is the God of Freedom, of defending the defenceless, assisting the poor, and standing up for the rights of the common man. But when taken to extremes, he is also the God of revolution, equality, and democracy, and as such is a constant danger to the status quo of the Empire. He is worshipped by rabble-rousers, democrats, cells of would-be revolutionaries and groups of brigands that steal from the wealthy to give to the impoverished. These worshippers are much of why the worship of Ranald is outright forbidden in Bretonnia, and viewed with so much suspicion elsewhere.
That's a bit of a leap, yeah?