Advise to build up userbase

Hi all

I have developed a facebook app in a niche that is quite big and has no big players yet.
The app was released about a month ago and has now 150 users.
I have a very hard time to build up a user base.

The users I have are very happy and suggest the app to others but the app doesnt take off.

My current stats are

MAU 150
DAU 20

What I did sofar to get more people:

- Facebook ads (PPI)
- Active community page
- Pinterest (the app is picture driven)
- Tumblr with IFTTT instagram pics and links
- Buy 200 likes so that the app doesnt look to empty
- Post on pages and groups on FB & G+ & reddit


The App uses:

- Like page
- Many share possibilities (share you stats, pics etc)
- Open graph
- Pin it
- Invite friends
- FacebookConnect / Canvas or registration via email


I think everything looks pretty good but the growth is horrible :S


Got ideas what else I could do?

Thanks!

I also tried instagram but my accounts gets disabled in no time when I try to post urls there ... ;o)

You will need to wait a little longer before it becomes stable or let's say 'Viral'. I push around 1k users in a few minutes and keep trying to get my app viral. If it fails on my first push, then I try again in another day. I would suggest you to post on few pages you own else buy a few status updates from reasonable pages which are active

Thx didnt thought about buying a post.
I also crosspromote on another app of mine (5k users).
I guess I have to be patient :-/

Any other ideas? ;o)