It's taken me 5 months to be as 'quick' as I am today. When I first started I was happy to be within +10 seconds of the Top 10. Now I'm consistently in and around +5-6 seconds.
So you're already ahead!
Consistency helps me. And that is basically a case of finding a car that suits your driving, that you are comfortable in and then just getting the best out of it. I'm sure I'll be corrected, but in my mind, the 'meta' car is only really good for 1 second tops in the higher echelons. We're talking about minor minor gains, really.
So what I've done over the last couple of months - in Gr.3 at least - is stick to 1 car, the AM Vantage. It might not be the 'quickest' or the 'meta' car that everyone else is driving for the top lap times. But frankly, if I keep driving it to the point it's symbiotic, it will get to a point that I'll either get it around the track as fast as that car can go, or the fastest I can drive.
It won't be top 10. But it'll be faster than a lot of people in DR/D can manage, whether they are driving the 'meta' or not.
That's my theory anyway