When I buy 'cook at home' poppadoms or order from a restaurant/takeaway they are usually very crispy and expand and bubble up as soon as you fry them. I tried a recipe for homemade poppadoms which consisted of gram flour and water (plus some seasoning and cumin), which I made into a dough and needed for a few minutes until it was smooth, rolled it into paper thin rounds, dried out gently then shallow-fried in about a cm of hot oil. They did not expand at all and turned out more like something between crackers and a flat bread. I'm guessing they need some kind of raising agent to make them like the restaurant style ones? Are these style of poppadoms easy to make at home? Does anyone know the best way to make them? 
I know this thread is a bit old, but just in case you are still struggling... You might be using the wrong flour. Papads are made from Urad Atta which is made from Urad Lentils, not from gram flour (besan) which is made from Chickpeas. It can be confusing because Urad Atta is sometimes called Black Gram Flour. If you can't find it, buy skinless urad lentils, dried ones, and grind it up in a spice grinder. I haven't tried, but I gather it works fine. Then to that you add a tsp of Papad Kharo, otherwise known as Bicarbonate of Soda, and flavour how you like. But Urad flour is essential. Good luck! 