With K&N or anything other part, remember.If it is rare, the cost will be more.
Please follow speed limits.They are in place for a reason.Just because you got lucky once doesn't mean you will get lucky a second time.If you have a pillion be extra careful.
If you want good mileage, trat your bike to an oil change every 5000kms( I use this interval in my car which has a company specified interval of 10000-15000kms) irrespective of what the manual says.
You can use servo or Hp or any other brand of oil.As long as you use new oil every 5000kms doesn't make a difference.
Fill fuel from one pump and one fuel station.If on a tight budget at the time its ok, but try to stick to one brand of fuel.If possible at any company owned-company run (COCO)pump of any brand.Try avoid pumps that are run by dealers.
Spark plugs, if availble use NGK platinum plugs.Iridium is too expensive and has very little to no difference compared to Platinum.
If your bike has a carburettor, get it cleaned.You can do this yourself by using a good quality carb cleaner spary or alternative try a fuel system cleaner.
Use a normal air filter.K&N filter are good for drag races and people who race, for daily drivers/riders its not a good idea since it allows a lot of particles into the carb(causing it to choke) and into the engine causing friction.
If you do not believe me check this link, they tested various brands of filters Air Filtration Test
All of the above should be available at less than Rs2000. Please follow speed limits.They are there for your safety and for the safety of other motorists.