I agree with you that person-to-person referrals are the best advertising. It's very inexpensive and very believable. Anything you can do to increase these is your best investment. Look into networking groups like BNI. Make friends with other quality tradespersons and offer to recommend them if they recommend you. Tell your current clients about your refer-a-friend program. Whenever you finish a job and you feel the client had a positive experience, offer to give them a small refund if they post a review online (but don't say positive review, just review). Verify it was posted, positive or negative, and then send them a check.
In my experience all print advertising is a waste of money. That includes newspapers, programs, brochures, billboards, and a wrap on your truck. If you must spend a lot of money to do a fancy ad on your truck, do only the back, the part that people stare at in traffic. People only take note of an ad when they have an immediate need, otherwise it's just noise they ignore. When people have an immediate need the first thing they do is type "electrician near me" into an internet search engine. Getting your name near the top of the search results is the key to getting calls, both residential and commercial.
Google and Bing both have multiple programs where you can pay to make this happen. You can also pay lead services like Home Advisor (who you already have a relationship with), Porch, and Yelp who capture a lot of leads with their own top of search result ads and resell them to you, but be careful, they are all a bit scammy. While you are paying for this, read up on SEO and do what it says (but be very careful hiring SEO companies, most are scams) to make your organic ranking better.
