$30 Heat Gun from Home Depot
$400 flash infrared
$1,000+ tunnel dryer.
what your production is going to be will determine the best dryer. Of course, the $30 one is the least reliable (is it always that way?

)
The flash is the most versatile because you will need one anyway even if you get a tunnel. The tunnel is good for production where you need to dry shirts quicker than 1 a minute (flash).