There are many many ways you can make money, the most popular ones are printing, mining and coinflipping.
When i started on SSRP, I used to print money and Uranium, and at the same time make Steel which i later used to craft various weapons and afterwards sold them, making a profit.
If you have an ALT account you can set it up to mine rubies, and automatically convert them into Gems in the process. Gems are used for crafting weapons, in updates to spin wheels which give you prizes, and also have a function as a "secondary currency" in the economy, they can be sold for 45$ (i think) currently.
I'd also suggest being on Server 1 during the following evenings as there were many events in which people who won were being awarded with items, cases, cash, weapons and other stuff.
Have fun!