Some of these things you could do yourself really quick for free and save money on SEO consultants.
For Technical SEO:
Google Lighthouse – use this to identify the area of focus for Technical SEO on your website. Send the report to your web developer with the exact request what you want them to fix. You can find an inexpensive web developer on Upwork.com
Use Markup Validation Service https://validator.w3.org to find out if your website has errors in HTML code. If it does (and most websites do) ask your web developer to reduce the number to a minimum.
Google Search Console – add your website and you will see if Google recognizes any errors on your website.You could use this tool as a source of truth for your website.
For Onsite SEO:
Use a tool called Screaming Frog SEO spider. It’s a free tool that you could download for free and run through your website in 5 minutes. Depending on the size of your website you could see the output of the tool pretty fast. The tool will scan your website and show you what Page Titles, Meta Descriptions and H1 tags are used. These are all important elements for onsite SEO. You could compare the output of the tool with the desired ranking of certain pages of your website on Google. For example, if you want to rank for “best plumber in Miami” you want to make sure that the page of your website that you want to rank contains that exact word combination in Page Title, Meta Description, and H1 tags. Screaming Frog SEO spider will help you identify mistakes with on-site SEO on your website.
For Offsite SEO:
Offsite SEO is about the quality and the quantity of links pointing from other sites on the Web to your website. For this part of SEO you want to check what backlinks you have, if you need to remove any of them because they are bad, or if you want to acquire more (you always want to acquire more links from high quality, relevant websites). In order to get the list of competitors backlinks you could use a free tool like linkminer.com Then you could check the backlinks of your website as well and compare the two lists to see links from which websites your competitor has that you don’t. If you find some interesting websites that you’d like to get links from try reaching out to them and ask if it’s possible.
The above methods is the simplest way to identify the SEO Mistakes on your website and improve your SEO.