jmeter - thread count limit

Hi

I have a question about thread count limit in jmeter. Some of the -
slightly older documentation on the internet - lists a number between
200-300 for number of threads. Some docs mention there is no hard fast
rule, it depends on system hardware/software config how soon the server
responds for APIs under test.

I have built a basic API test plan for a mobile/server type of application
tested for 2 users in csv file thread count = 10. We now need to put
more load on it I was checking out for any guide lines here. What are my
options? A + B or just one of them? Are there any other options?
A. Increase number of users in csv file
B. Increase thread count

Thanks
SK