Hey there.
Thanks for question.
Online streaming needs at least 1 Mbps connection. 3G, 4G or ADSL (other similar).
VIDEO STREAMING
For Online Video in SD Quality 360P you need at least 0.5 Mbps / 0.5 Mbps Internet connection.
For Online Video in SD Qaulity 480P you need at least 1 Mbps / 0.5 Mbps Internet connection.
For HD 720P it is 3 Mbps and HD 1080P 5 Mbps according to YouTube. Upload speed can be even lower, it is less needed on streaming.
MUSIC STREAMING
For music in 160 kbps quality you need at least 384 kbps / 384 kbps Internet connection.
For music in 320 kbps quality you need at least 512 kbps / 512 kbps internet connection.
For music in lossless quality you need at least 2 Mbps / 0.5 Mbps Internet connection (4G or stable). 3G may not work due to high needs for Internet every second.
ONLINE CALLS
For voice calls you need 56 kbps / 56 kbps Internet connection.
For video calls you need at least 512 kbps /256 kbps. The higher download and upload is, the better is quality, up to HD.
I use Mobile network, 3G Unlimited, 1M/0.5M and every service seems to work well. So if you watch also online sites like YouTube or Dailymotion. Or you do often video calls abroad for free, just get something near 1 Mbps.
Please note these speeds are per stream. If you have many devices at once in your modem, probsbly you need to pay for more speed. For example if your 3G connection is 512 kbps / 512 kbps Unlimited, you are only able to stream Spotify in 320 kbps and any surfing on Chrome will make stream going loco in no time. To reduce that, just use Offline mode in Spotify Premium. so you'll have then FULL speed for other things, like Chrome surfing. That's the thing I do on my phone and laptop, as my 3G is main connection.
My speed is this, 9.90 € month, unlimited.

I hope you will have a nice stream. Merry christmas!
Kind regards.