1988 Toyota Tercel 2 door Hatchback gas MPG problem

So i just bought this car off craigslist for a 1000 bucks, and it works great. it did have a problem, where the car turned off it would act as if it kept running, the mechanic said it was the carbourater gasket plate and he replaced it for 200 bucks, he also said it would help with my gas MPG, but it hasnt changed at all. I currently get about 190 miles out of a tank, i feel this is extreamly low, i was wondering if anyone could tell me how much i should be getting MPG wise with this car and what the problem might be? its a little shakey when it starts up. its a automatic transmisson, thanks.