I have tried almost everything trying to get sign ups, facebook ads, adwords etc. But the cost is too high and also not too much sign ups.
The most effective way to get sign ups for free or at low cost is that you set up a blog, target your desired audience through its content and then while you have trust ask them simply to sign up.
What kind of sign-ups are trying to get exactly?
I just wanted to sell my tutorial on painting.
Use small videos in youtube. Now-a-days those are a pretty huge hits in the art section. It will only take your mobile so its very cost effective.
Show your tutorial painting in different ways like in an interesting content within a blog site post or an amazing video content.