Can I mine bitcoin with a gaming computer?
It is not profitable to mine Bitcoin with computer(s) and GPU(s). If you just want to help secure the network and/or keep your place warm in a high-tech way, then you could mine Bitcoin ;)

It could be profitable for you to mine some other coin, using your computer and GPU(s). You could also set your computer up to rent its computing power to others by joining services like miningrigrentals.com

For GPU mining have in mind that the more GPUs you have, the better. Since you don't pay the cost of electricity, you might want to add more GPUs to your computer. Just make sure the Power Supply Unit (PSU) can handle them.