Is a chromebook great for gaming?

Chromebook's can only download items from the chrome webstore, which is limited.

Windows are the best gaming desktops/laptops.

"Chromebook" officially means laptop running Google Chrome instead of Windows.
I don't know about of DirectX, but Steam may be supported if you confirm that.
Minecraft and Roblox are very low resource need games so if software compatible just about any new laptop runs them. It takes a bit more graphics and cpu processing to run at max.

Microsoft has reduced their pricing to the OEM companies selling branded laptops, and the cost different from Windows to Chrome is officially about $20 or so.
Your country and price point would allow me to recommend something. Be advised that normally, as price goes down, both performance and quality-reliability drop. Also keep an eye on storage size.
cpu benchmarking
https://www.cpubenchmark.net/...u_list.php
graphics processing on the second tab page, or better:
gaming to GPU
http://www.notebookcheck.net/...849.0.html

Any laptop with only 16 or 32GB of SSD storage and no HDD will be used mostly online.

http://www.bestbuy.com/...Id=6497029
Acer Chromebook at $450
i3-5005U, 4GB RAM, no optical drive, 15.6" 1366x768 display, 32GB SSD

http://www.bestbuy.com/...Id=4352000
Asus Windows 10 laptop at $330
i3-5020U (11% faster CPU, same cpu as clocked a little higher and graphics turbo frequency slightly higher) 4GB ram, 1TB spinning HDD, optical drive, 15.6" same
The 1tb hdd and 32gb ssd now cost about the same

Microsoft has offered a win-10 version to cheap netbooks for next to nothing. You get better performance in chrome, but much less versatility at the same specs.

Wait until ready to buy, then ask. Prices change weekly. Include your country.