You find many great playlists on the forum that you can import for free without registering on the forum. 
In iReal Pro, tap on Forums and on the top of the screen "Quickly download Main Playlists" to import them. Here is an example on the iPhone:
Here are a few playlists to start with:
Click here to download the 6 main playlists.

You find detailed instructions how to import songs here.

In case you’re looking for a specific song:
On your phone/tablet:
tap on the Forums (globe icon), then the magnifying glass on the top right and type the title in the Google Custom Search field.

On computer:
Go to the iReal Pro Forum and on the top left, type in the title in the Google Custom Search field.

If you don’t find the song, you can post a question and maybe other iReal Pro users have it.