Estimate servers architecture (hits, traffic,droplets size)

Hello,

I was just wondering how can I correctly estimate my servers needs. I have a website done with PHP and MySQL ( replaceble with mariaDB ).

Each page is on average around 300-400Kb

I have 3 user types:

1) Simple user

• will visit 6 pages
• will spend 2-5 minutes

2) Average user

• will visit 10-15 pages
• will spend 5-12minutes

3) Heavy user

• will visit 15-30 pages
• will spend 12-25minutes

In our beta-testing period we estimate to have around 200 users the first 2weeks and around 1000users in the first 2 months, most of them coming from USA (same timezone).

The question is:

A) how can I start ? B) how can I scale ?

This is my idea, please comment:

A) DB srv => 1Mb droplet (if needed I can scale to 2Mb droplet) Automatic daily DB backup on other FTP server. webserver => 512Mb droplet (if needed I can scale to 1Mb droplet)

How much traffic will this setup handles ? My BADGET: $30/mo

B) DB srv => 2Mb droplet Automatic DB backup every day, live replica on a smaller droplet? LoadBalancer => 512Mb droplet web1 => 512Mb droplet web2 => 512Mb droplet web3 => 512Mb droplet

My BADGET: $50/mo

Will this architecture handle 10.000 users? what about 20.000 ? My concern is about the DB srv, is that enought? should I go on a dedicated machine (master) with a slave on a 1Mb/2Mb droplet ? Should I keep everything whitin DO infrastraction?

thank you