Hi Artnimay and welcome.
As with Ben’s post, you will soon get the feel of when a blades require changing, with some hard woods, this can be after only a few minuets of cutting.
I purchase all of my blades from Hegner, this is not because I have a Hegner saw, but because I find their price is competitive when you purchase a gross or more at a time. You my think at this time that a gross is a lot, but if you get into cutting a lot, and you will, as scroll sawing is addictive then purchasing blades by the gross is the way to go.
The blades I use are Niqua, have done for many years and for most cutting, I use 3, 5 and 7, reverse tooth.
Take care and enjoy your scroll sawing. :wink:
Chris R.