What do I need for facebook Audio Live streaming? I would like to do audio live streaming on facebook.
I intend to get audio feed from myself, from a guest sitting next to me, from a guest over the phone and a guest on Skype. And then stream it on facebook.

In terms of equipments: I got a laptop which has 8th Gen Intel® Core™ i7-8550U mobile processor, 12GB Memory and Intel® HD Graphics 620
An internet connection which has upload speed 300 kbs to 1.2 mbs. (Not steady :( but enough for audio, I think.)

I got OBS software, but it is designed for video transmission not audio.

What else do I need?
Any equipment, software, etc?
I would consider just using your phone (use Wi-Fi depending on situation) :) 

I found this great video of how to do Facebook Live Audio cast (click here).

For your situation I find it quite suitable to use your phone instead of your laptop. It will make it easier since both you and the guest are using a phone. Then it makes the whole process seamless.  

You can buy external stereo mics for phones to improve audio drastically.   

You can gradually build up a better setup over time once you get more comfortable with Facebook live. To be very good... it takes time :)

Try to have at least a 5-10mbps for a video live stream.