What is the best pc case with good airflow,graphic card up to 28 cm,mid tower and cheap?

[Abxolute]

A case that is compatible with msi z170a pc mate?

 

[maxalge]

A case that is compatible with msi z170a pc mate?

http://www.amazon.com/dp/B00I0MKMG2/ref=psdc_572238_t2_B00EWHOIN2

 

[geofelt]

Your motherboard is a full ATX and needs a full size case.
If you can use a smaller/cheaper M-ATX version, you will have added choices.

My criteria for a good gaming case would be one that has at least two 120/140mm front intake fans behind a washable filter.
That is sufficient cooling for any single gpu gamer, and the filters will keep your case cool.
Silverstone makes excellent quality units, here is a SilverStone Precision SST-PS13B for $45
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163352
You will probably want to add a second 120mm intake fan.