Bitcoind server strategy. How much disk space? I need to host a Bitcoind on a VPS. 

My main issue is the disk space strategy. I don't know the amount of MB the blockchain adds per day or per month.

On my disk I have 26GB of disk spent for the Bitcoin installation. There are some numbers about ho much the blockchain will add in disk space over time?

I'm also looking for VPS with a lot of disk space on the cheap. If you have some advise on this, I will appreciate.

Best Regards,
Hosting Bitcoind on a VPS is a very bad idea. I cannot stress this enough. The VPS provider will not have adequate security standards. You increase your risk profile dramatically as the combination of software running on the host server can cause a problem for you and your users. Please. Don't.

That said, if you do want to, it all depends on how transactions will be dealt with in the future. As a VPS is usually fairly flexible I'd take about twice the blockchain now, and just upgrade when you're above 80% disk space usage. That gives you some wiggle room.

You may consider using a light client, perhaps with increased connection count (more than 8). That will totally remove your disk space hunger and it's reasonably secure.