Gaming laptops are unfortunately not cheap. Depending on where you live, have you checked Craigslist, or the local Buy/Sell/Trade pages on Facebook?
If those are both not an option, you would have to save/earn some cash. Unfortunately, you have to work to earn money. Linus actually made a couple videos on how to do this (Look below). When I was your age(12), I mowed 4 yards, $20 a yard, every 12 days per yard. At the end of the season, I was able to purchase the parts for my ATV while still being able to take out a few bucks for a soda or candy bar. Depending on where you are located, the options below may not be an option. Try walking some of your neighbors dogs or watering plants. Talk to who you live with to see if you could get an allowance for some chores. Ask for cash for your Birthday or other holidays instead of presents (you may need to return the item to get the cash.)
Mowing Lawns:
Picking Blueberries: