I don’t think that Miata is good for drift, it is too small and short. But I know what to do:
1. Get some good tires. A 195/55/14 is a great match for the stock 14″ wheels on a Miata (NA and NB). Toyo or Falken (195/60/14). It won’t be a problem, 14-inch wheels are cheap.
2. Get a GOOD alignment done by a shop that specializes in performance alignments. A factory alignment is simply not appropriate for any kind of aggressive driving.
3. Make sure your maintenance is up to date and the car is solid. Miatas are built to be driven hard, but no car puts up with both being driven hard and being neglected. Ensure that a good tuneup is done on the vehicle and there are no outstanding maintenance issues on the car.
After you have some seat time in a stock Miata with tires and alignment, then I’d endorse the LSD first (expensive, but will have a huge effect on the car), then stiffer springs and sway bars paired with Good adjustable shocks (or coilovers depending on your budget.) Supercharging or turbocharging the engine will definitely help in the power department, but I’ve always felt that part of the appeal of driving a Miata is doing more with less. The lack of power forces you to become that much better so you can wring every ounce out of the humble car without the benefit of having a lot of power.