You'll probably get hassled if you start over-using the introduceyourself tag - it's tag spam and frowned upon by many in the community.

Other than that, keep working hard. You're right about it being more quality than quantity but if you can do both... Original posts of your own should be high quality but I'd limit these at the start. Comment on other people's posts, instead. You can do these a lot quicker (whilst keeping the standards up) and if you're helpful / pleasant to interact with / interesting, you WILL attract followers.

I'm no expert and I'm clueless as to what the threshold is going to be. But if a lot of people are thinking highly of you and then you try increasing your posts a little, you might suddenly find your rewards increase.

Just don't ever give up! ;)

Good luck.