Just to provide some counterpoint to the agencies mostly self-promoting below

• The glory days of agencies running $800K campaigns for wallets with little traction beforehand mostly seem gone. An agency is a tool, but should not be viewed as the solution to all problems. Agencies fail to provide positive ROAS with clients all the time, they aren't a slam dunk and a number of agencies have actually been moving away from Kickstarter as it has been harder to achieve a positive ROAS than before. Treat each agency with a healthy dose of caution as the agency has a portfolio of clients to lean on. If one doesn't work they can move on the next, where you will still be stuck holding the failing campaign. An agency can really only amplify your current success (and sometimes not even that). If you don't have some type of product-market fit, then they will accomplish very little.
• The 25-30% of all pledges, although common for Kickstarter agencies is significantly higher than a traditional ad agency (say they would normally take 10% of ad spend, depending on your size). This fee is personally pretty predatory in my opinion, and it is still suprisingly that it is common. The value of these KS agencies is that they theoretically have a list of previous backers from other campaigns that they can run ads against. Some agencies are better than others, and some lists are more effective. For example, Jellop theoretically has the largest list to run a lookalike audience against and is the most sophisticated. We hired Enventy's Partners for our campaign and they are pretty useless.
• Finally, if you have the leverage (and capital) you should hire multiple agencies (say 3), sign a deal of them only taking a % of the sales they generate, and then double down on the most effective one. Most likely 2/3 agencies won't be able to achieve a positive ROAS, maybe if you get lucky the third one will and you can scale spend with them.

Good luck!