Gain and volume are often used interchangeably. The thing about it though with mics is that the higher the gain, the more distortion in the audio you will get. If you have to turn the gain up to 100 because it's too quiet with the C01U, then you're simply too far from the mic. The further you are from the mic, the less force your audio source (voice) is hitting the mic diaphragm with. And thus the quieter it sounds. It's just like headphones and speakers. Most sound great from low volume up to about 70-80% of max. Go above that and the sound starts to break up a bit.
6-8 inches from your face is the distance most condenser mics are designed to be used at.
Once you've got it positioned correctly, then you can look into audio adjustments. It's easy enough to look up tutorials online. If you record some blank audio before you start speaking, that gives a benchmark audio pattern of what the background noise in your room sounds like. Then in Audacity, under effects there is one called Noise Removal. So you can select that pattern where just the noise is present, and remove it from the rest of the track. You just want to be a bit careful because the more audio you remove, the more robotic the sound will become. Google Audacity and Noise Removal and you'll find plenty of tutorials.