What kind of vent material can be used for gas dryer?
The best choice is metal hard wall duct. 

It is smooth inside and does not cause lint to build up.

Lint build up can be a bit of a fire hazard and leads to restriction of air flow that is exhausting moisture. That leads to extended drying times. 

If you must use flex get the semi rigid type and be careful not to crush the shape when making turns.