The number of ships is not the most relevant factor with the Neinzul. They always have a lot of ships. No, what are far more important are delaying those ships, and ensuring you have the right ship types to eat them up.
I'd recommend gravitational, lightning and flak turrets, for sure; plus as many fighters as you can with a light starship or two; anything else you might have which does area of effect damage; and then, depending on the types of Neinzul you're seeing, missile, MLRS or laser turrets, raid starships or bombers. Snipers are always good but they'll really put a strain on your economy so early on.
Best to do what you can with a couple of strategically placed gravitational turrets, a healthy number of fighters with a light starship (or two) and as many turrets as you can feasibly support that early on, especially lightning and flak.