Getting tons of refs is actually quite easy, considering most of the GPT sites gives you campaign features.
You can buy 1000 clicks as low as 10000 satos and easily get 10 to 50 refs, depending on many factors like countries, day, time of the day, etc.

If site A brings you 10000 satos, simply invest your income to get more refs on site B. On this one, wait to have your 10000 satos and invest them to gain more refs on site B; repeat day after day. This may look easy as there is an obvious snowball effect, but this is much more complicated than it looks. Your main issue will be the productivity of your refs.

To get it, simply get your daily income and divide it by your number of refs. Some sites give you good productivity, like 30 to 50 for instance (my own figures, may really differ from one user to another one). But other are terrible leaving your productivity below 10. Simply avoid them. Having a campaign from site A targeting site B will give different results and productivity if you run a campaign from site C targeting the same site B.

You need to test as many combinations as you can, using split testing. But after several failures, you should clearly see what is working and what is not working. You should also renew your refs since after a while some of them are done with their claims, cash out and leave the site. Your productivity will give you this signal.

The keys are patience, testing, arbitrage and having a strict accounting of your figures, especially this bloody productivity.

Hope this helps.
Regards