Results can take 3 – 6 months and even then depending on the starting point results don’t necessarily mean high ranks. We need to know more about your business/the landscape of your industry. $600 could be a decent budget, or it could be basically nothing if you’re competing against businesses that have monthly budgets in the thousands.
The most important thing is if you’re struggling and using SEO as a Hail Mary you’re going to be disappointed. I’d recommend going back to your SEM campaign if this is the case as results are more instantaneous and you already have achieved results with it.
The SEO and site overhaul was done in September…as in last month or September 2019?
If it was just done last month, you still have about a 6-9 month runway to start seeing things ramp up. This is just a blind assessment from my end without actually seeing the website. There’s a chance that what you think was an “overhaul” might not be good enough of an overhaul from a consultant’s perspective.
It sounds like you need quick results though, which in the case I would continue running PPC with any budget you can. SEO absolutely needs to be done, but if your knuckles are turning white from anxiety about not seeing enough growth then you’ll need to stick with paid advertising for the short term.