How we can improve Fuel consumption of Kia Sportage 2014. Also guide me what is the Avg fuel economy of Kia sportage 2014 with 50,000/ mileage. Does changing of spark plugs have any affect?
Seeing as how most vehicles made today dont need any tune up done to them until 100k miles, there's nothing you can do to your vehicle to get better fuel mileage as far as a tune up goes. You could possible do things which are extraordinary, such as get mechanical work done (ie: cams or porting on heads) or tuning (new fuel map).
As far as a tune up, the only thing which can get you better fuel mileage is by tuning up the driver (as Solar Mike stated in comments). You'll have to decide what is the best way to handle that.
If there's nothing you can do on your end, the only thing left is to get a more fuel efficient vehicle.
Unfortunately, the Kia Sportage isn't the most fuel efficient vehicle even when new. 21-23 MPG combined depending on your trim: https://www.fueleconomy.gov/Feg/bymodel/2014_Kia_Sportage.shtml
Like solar-mike said, drive gently and follow your service schedule. Try not to accelerate quickly, coast as much as you can, and try to avoid braking.
If you have 50,000 miles on your Sportage, a new air filter might make a tiny bit of MPG difference if your current filter is dirty. New spark plugs could also make a little difference but would basically only be noticeable if your current ones are old or wearing out.