Any backlinks you buy are likely to be low-quality and that can hurt your rank and reputation with Google far more than it helps. Once your site gets penalized by Google it will take time and $$ to hire someone to help, and it will be far more money spent than you did on the links.
Instead, follow whitehat practices.
Create quality content. Make sure your site loads fast. Build relationships and earn links with your content.
As for hiring a consultant, it really depends on A) What you want and B) What your budget is. There is no shortage of people offering SEO services, but there is a wide range in what they can do and the quality of work they can provide.
If you're looking for a lower-budget offering try Upwork or Reddit, if you want to work with a more established firm Google is your best friend (as are agency listing sites like Clutch.co).
Do not buy backlinks.
Any backlinks you buy are likely to be low-quality and that can hurt your rank and reputation with Google far more than it helps. Once your site gets penalized by Google it will take time and $$ to hire someone to help, and it will be far more money spent than you did on the links.
Instead, follow whitehat practices.
Create quality content. Make sure your site loads fast. Build relationships and earn links with your content.
As for hiring a consultant, it really depends on A) What you want and B) What your budget is. There is no shortage of people offering SEO services, but there is a wide range in what they can do and the quality of work they can provide.
If you're looking for a lower-budget offering try Upwork or Reddit, if you want to work with a more established firm Google is your best friend (as are agency listing sites like Clutch.co).