Increase amount of traffic

So I started running a SEO campaign for a locksmith business, I have been reading a lot of guide about ON page editing, and I have partial control over the pages, I'm not trying to compite in a very high keywords values, and only in local area, I got the website to the first 2 pages but since then it went down to the 3rd page on 2 of the main search keywords there is no news or updates I can really do on locksmith world at least not daily or weekly theres nothing to update, I have been keyword researching and im changing words and researching every once in a few days if the words change, using google tools. I got Moz crawl diagnostic results and im getting errors that I think doesnt exist, for example Too many on-page links on pages with no links at all, or title element too long when its not most errors are Rel Canonical but i have no idea how to fix them, also how many of you think meta description is worth writing? I'm getting possitive and negitive comments about it, last thing I want to say is, I got a 200$ monthly budget to SEO this website and would like to know where should i invest these 200$ every month to promote it to the first page, I'am not looking for someone to do my work for me but for useful tips, I have thought about buying moz advance program for 100$ a month but not quiet sure if that what I even need.

this locksmith campaign

https://surelockkey.com/

is the only one I'm running because its my own family business..