Forgetting about the gourd contraption, yerba mate is quite delicious and can be prepared the same way as with loose tea leaves, by using an infuser or even a French coffee press. Just be sure the water is hot but below boiling temperature, else you'll get a bitter brew. Two level teaspoons of yerba mate per 8 oz water is about right. Add milk and sugar to taste.
You'll find yerba mate on the shelf in your neighborhood latino grocery or many supermarkets carrying hispanic foods. A 2 kilo box of Nobleza Gaucha brand or simililar should be less than $3.00, unless you buy it online where the price is double (plus shipping). Yerba mate also comes packaged in tea bags, plain or flavored.