Some tips using Hangout, this is basically my experience so pardon for the lack of sources.
Hangouts seems to work even with just 40 kbps (40 max download or upload). Note that bandwidth can be unreliable dropping off when more people in the area use up internet. The 40kbps is my PLDT (isp) copper wire Internet that is parallel my land line for about $20usd/month. A good wifi router is also a factor, from experience of trying various other brands (TP link and D link) Cisco has performed the best. Remember to reset your router and if you don't secure it beyond password, change the password when there is an inconsistency to it on wifi versus direct hard wire connection.
Of course the more bandwidth the better but there are some little things that improve the experience.
Note: sound is data, reduce it and you reduce the bandwidth you need. Reducing ambient noise reduces the data you need, so Noise Canceling Mics are very handy and when you speak into your phone you may want to put the phone close to your face (and turn off the face camera).
Self mute yourself when your not talking, it prevents noise from creeping in. Feedback can build up slowly and steadily, I've seen it happen in games glad I took Audio mixing in college since the science of this is pretty hard to default from other skills.
Earphones prevent the sound from your speakers that will build up feed backing into the discussion and overloading the system. Background noise is bad, I've learned not to take it badly if the guys have to mute me when I could not mute myself when I have to do somethings. I don't like muting people, but sometimes I find it that its needed because of the feed back. the technical requirement of earphones is strange because its prevents feedback but many don't want to impose the technical requirement.
If people can't hear you, maybe turn off your face cam or ask them to turn off their face cam. The camera does add to the bandwidth requirement, both upload and downloads.
Often I just used the PLDT internet when I'm using G+ and will have my Roll20 app open. Of course I have to cut down on tabs and in many other things. Our Philcom internet is MUCH faster being able to have a consistent 300kbps and allows me to run my games with little lag. I run my games at 7am on Saturday so I get to use the best internet for the day despite the Huge maps I use in my games.
Internet is pretty much about Luck or Bureaucracy. Some places have really good internet because they area has good infra because of BPOs here in the Philippines. Some have really good internet because its just so profitable, like our building here and 3 ISP providers are offering internet.
Some places have good internet even they are pretty far from all these ideals, while I have a friend who's family and residences is supposed to be a premier living place for Expats but has crap for internet (I bet the residences lost a lot of clients this way). The way I know how he could fix his situation is have his building put pressure on their ISP (yup the development company also owns the ISP that is giving crap internet). You need to know the org chart and roles, and be on top of that until they deliver (by on top, detailed report why they failed to deliver).
Other places and the friend of mine can benefit from a Potato Mesh ($99+ delivery cost cheaper when bought in bulk). Particularly having two Potato Mesh devices (up to 3MBps), making a wireless connection. Although its wastefull for my friend, since the building should have good internet in the first place.