PS: my contact information is in my profile in case you want to exchange about this. Please add the link to this thread so I can mentally load the state.
I'd say ads aren't a strategy, but a tool/tactic you can use both for 2C and 2B in combination with other tactics under a general strategy.
One thing to think about is the complexity of your product's sale on the spectrum: self service, low touch, "medium-touch", high-touch? This depends on several things, price being one of them. You can also reduce the complexity of the sale through design and technical means until its irreducible form at a given price point.
The word is "combination", as even with "2B", you'll tend to have a combination of several tactics for different reasons. You may go with self-service where people can just put a credit-card to access a stripped-down version of the product to drive adoption, but your revenue may really be driven by doing high-touch with enterprise clients who may want to do on-premises deployment because they work on sensitive/classified projects. You're doing one both, but not for the same reasons.
"Expensive" is relative: different people have different discretionary spendings and the way you price your product and the segment you're trying to sell into will influence your sales process. You're trying to sell a $300 product to someone who works in role A, and they'll need their manager to sign off on it. You sell another $300 product to someone who works in role B, and they can just buy it without consulting anyone. You sell a $1,500 to that same person, and it's not them anymore who will decide. You sell for a certain sector? They won't do that at all: they'll want to do an annual contract, procurement, legal, security, and a bunch of other people will be involved. You'll need SLAs and many acronyms will be thrown around.
The complexity of your sales also depends on the complexity of your product: does your product do something rather obvious that everyone "gets" (email marketing, invoicing, accounting, photo sharing, communication) or does it do something that's rather complex that requires education or that doesn't even have a name it. That, too, will influence what you will end up doing.
Is your product targeted towards a profession that may have a governing body or an order or something? You may then talk directly with the chamber of commerce and get a list of clients, or talk with the Order of Physicians or an equivalent for the sector you want to target.
It depends who you're talking with, too. You may be talking with an engineer who is not the "economic buyer", even if your product is self service: they work on sensitive and classified information and can just not use your product like that, so you need to meet with the people mentioned above and answer a bunch of questions.
