buying stashes via steam

hi guy
im a player from tunisia. we have no international credit card so we cant buy anything on the web except on tunisian website but we have finally introduced steam gift card in the country.
so i wanted to know if its possible to buy tabs via steam. and if yes can someone explain to me how pls; not really used to buying things on the net. been playing since blight league and having no premium and currency tabs is a pain.