This is according to how heavy your pages are. First you calculate your page rate. 30K/ day is roughly 1 page every 3 seconds, BUT you may well have times of day with 10 times more visitors than the average. Therefore multiply by 10 and assume you have a peak load of 3 pages per second.

Some people's pages have 4 or 5 elements, others can have 100 or more elements per page. So, going with a worst case type measure, you may have 100 static elements per page, and 3 pieces of dynamic dynamic content per page.

That gets you to 30 static elements per second and 1 dynamic content piece per second.

Apache on a single CPU should be able to handle that. however the db and or apache may consume more than 512 MB. I'd go with the 1 GB plan myself.

Then I would install atop to monitor the system performance over time.

http://www.slideshare.net/modoc/apache-performance-12508773

Gives some indication of the abilities of modern web servers. Look around page 10 of the presentation.

To provide you w/solid recommendations, you need to provide more details:

How much static vs dynamic content will the droplet serve?

Are your site visitors disbursed all over the globe or are they concentrated to a specific geographic area?

Are you willing to pay for a high availability (HA) configuration (in the form of additional droplets)?

Thanks so much wwalker!! Your answer brought me some light!

Pablo, i still don't know how much static vs dynamic content it willl serve =( My site is www.pergunteaumamulher.com

My visitors are 90% from Brazil.

I can't tell you abou hiogh availability also, i still don't know what it could mean, but i'm seriosly thinking about splitting, one droplet to my site, and another only for hosting podcasts (.mp3) files

What you guys think??

Thanks so much!!

No body can answer this question as no body knows how your app is written, what the average memory usage per request is, etc..

It depends on a lot of factors. I suggest you start with a 1GB droplet and see how your app performs and then scale up as needed.

Totally agree w/@Kamal; so what follows are more educational recommendations as opposed to suggestions on what to do w/your specific site. Check out:

1.) How To Set Up Nginx Load Balancing;

2.) How To Install Wordpress, Nginx, PHP, and Varnish on Ubuntu 12.04;

3.) 10 Million hits a day with WordPress using a $15 server;

4.) The Importance of Caching WordPress;

5.) Amazon CloudFront.

If you're thinking about splitting up your site across various droplets, however, I would definitely recommend a configuration-management tool. See How To Install Puppet on a DigitalOcean VPS.