Population

What are the best methods for gaining population. I need 2 million people to increase my Game Level to 3. I would like to try to not use gold coins but I will if necessary.

-Rich

Well, when two sims really love each other very much...

Are you new here? New players need only log in twice a day and they get a little prize. Either $400B, or 300K people.
If you're not, well then, you already knew that.
I've never managed to figure out how to speed up population growth organically. I imagine there's a few ways to screw it up, like not having any hospitals, getting into a major war, that kind of stuff. But other than the joke, I'm of pretty limited help.

Conquer a C3, steal their pops with the exchange professionals button.

OK, I looked into the transfer button. To transfer people, it says the other country population can't go below 100M. Since my conquered 'slave state' has only 14M, I'll be waiting a very long time.
But you said 'transfer professionals'. I can't find that...

Also,
You can click on "direct trading" (on left), Click on "Population Transfers", and then click on "bid coins for population transfers". You can bid gold coins for 1M people. The problem being, the minimum bid is 6GC, and almost nobody ever wants to pay that much.

In your country, at the top, go to labor, exchange professionals with other country. Type in the name of the c3 your conquered. You can move 200k people at a time from the c3 into your country. You can do up to 400k total in a game month between countries you control. You do not need to move any from your main country into the c3. Just do a one-way transfer.
Repeat this every game month and you will increase your population quickly. Remember to destroy all the corps in the c3 when you are warring it so it will free all those workers. You have to wait a game month after winning for those workers to be available but you will have some free immediately after winning.