G+ is a busy place, you just have to get your circles loaded, find those who are active at the right hours, and engage. During the day, depending on where you're from, most people are at work so it's hit and miss. In the evenings they're with family, still hit and miss. Late night, you get a busy night crowd but mostly you have to find those who spend their time online more than offline to really engage actively. Like real life though, the weekends are the busiest.