I'm not a regular gamer i used to play lot of games during my holidays in my ps3, so i thought of upgrading to ps4, but some of my friends said me to buy a gaming laptop so please help me here to find the best laptop or is there any other thing?
Lenovo y50-70 or alienware 14 or 17?
Get the lenovo y50. Never ever get alienware.
Never get Alienware. They use budget-grade components, leading to faster burnout and system failure.
As to a gaming system, I strongly recommend steering clear of laptops entirely. (1) Thin body means restricted airflow on heat-sensitive components, faster buildup of dust, and a higher failure rate for primary components [CPU, graphics cards, especially]; (2) Thermal and space requirements mean you pay far more for far less power; (3) the odds of you ever taking the thing out of your house is slim to none. When I was in college I bought a gaming laptop, and the thing was burned out and useless within two years. Poor investment of $1200. My desktop on the other hand still uses the same case after eight years, and after two upgrades the original components still work thanks to regular cleaning and aftermarket coolers.
If space and ability to move to/from a college dorm or apartment is a concern, consider instead building a micro-ATX tower and going that route. You will have an excellent, stable gaming rig for about $400 less than the laptop and have the ability to upgrade as new technology comes available.