Guess who works for NotaryReviews.org, I've been a notary for 16 years, and have never paid to me listed or gain access to some company's website to get business.
To answer your question:
You need to focus on the entire US. I get orders from all over the country. All that matter is that your doing the signing in your state that you hold your notary cert. in. Focusing on only signing up with high paying companies, you will go broke. You need to have low paying companies mixed in with some high paying companies. The key is getting your daily signing orders between 3 to 7 per day or more.
Title companies pay the highest (but they like hiring signing companies to provide the notary), Escrow companies pay the next highest (same on the signing company), Signing companies are the lowest payers.
Sign up with all of them, You need volume and experience. Over time you can pick and choose who you want work for.