I figure this may depend also on what sort of product do you want to advertise.
Such as If it's strictly online, if it's online retail (aka physical product sold online), or whether it is an actual physical location.
A) If it's strictly online, like a subscription service, software or an APP, then you may want to probably focus most of your advertising budget on online, since you want the person to act instantly, on a device, where the ad is displayed.
B) If it's online retail than it could make sense to highlight the current bestsellers or best offers also with offline advertising (as the ads for online retail shops in a Subway / Tube) as these appeal to the general public (aka a special discount on a notebook etc.) and you may want to approach regular consumers looking for deals also offline.
For example someone looking to buy a new TV set is high likely to be curious about any given ad featuring a deal for a new TV, no matter if he sees it on his device, or whether he sees it offline.
C) If it's a physical location, then of course you need to go with a mix of online and traditional offline marketing, banners, shields - there are all sorts of out of the box options too.
I did, for example, marketing for a chain of GYMS in Germany, and it was a mix of Google advertising, social media advertising, social media and Google my Business presence.
Plus also a traditional approach such as shields, banners, flyers, giveaways, promotion at a leisure time oriented events etc.
Including QR codes for a test training or for the GYM's url implemented in all physical advertising parts, where suitable.