There's no single right number, but a useful rule of thumb for established remodeling businesses is 5–10% of revenue on marketing, weighted toward channels with a track record (referrals, local SEO) and a smaller test budget for newer channels like paid ads.
For a newer or growing business, that ratio often needs to be higher temporarily - closer to 10–15% - to build the local SEO foundation and review base that pays off for years afterward. Think of the first few months less as a marketing expense and more as building an asset.
One number worth anchoring to: the value of a single job you'd otherwise lose. If your average kitchen job is $30k, spending even a few thousand dollars to make sure you never lose one to a slow reply or invisible Google presence is a straightforward trade.