The firm that works along the lines of user targeting seems to provide the best results.
Make sure the agency has experts who are informed of the best SEO and SMO marketing techniques plying in the market to give accurate results.
The agency provides other services as well like, social media marketing, content marketing, marketing research, email marketing, web design, and development, etc.
The agency should have a valid certification and works with a team of experienced and professional people.
For more details: https://www.elsadinc.com/seo-smo-marketing/