Buying art supplies in Gulshan is not easy as easy as buying art. There is one store in Landmark mall (on the ground floor in the right hallway) in Gulshan 2 circle. They have canvasses and oil paint, etc. But if you want to buy fine point drawing pens and art paper in different grades and weights, then head to New Market. The art stores like Modern and ABC are located near each other by the south gate, also known as Book gate, of New Market. Coming from Gulshan, you drive between Chawdni Chowk and New Market, then make a right turn. There are art supply stores in Old Dhaka but that requires more time. And as always, go on a Friday so that the trip will not take so long. Some of the stores are closed for Friday prayer so after 2 pm is best.
One thing about shopping. Make sure to ask for the cheapest items. For example, we asked for poster size water color paper. They showed us the 250 taka German brand, the 120 made in Britain brand, but did not show us the 60 taka Chinese brand until later. The store owners understand a fair amount of English which is nice but you still need to persevere to get the cheaper options explained to you. All the prices are still cheaper than in Gulshan. The stores have lots of really nice supplies which is a delight to find in Dhaka.
Also on “book street” in New Market, are several wedding invitation stores.