Getting your microphone volume just right is an important step for streaming since it's one of the most direct ways you interact with your audience. If they can't understand what you're saying, then it's going to be hard for them to talk to you or listen to you react to your game!
There are a number of options in Gamecaster to help manage your microphone, but even before you start streaming there are some tips you do to help improve your noise situation:
Your environment is everything. Even if you have the most expensive microphone you can buy, it can't save your audio from a noisy streaming space. Try and minimize loud things in your area like fans or a clicky keyboard!
Practice good microphone habits. Make sure you're speaking into the correct part of your microphone, keep it a few inches away from your mouth and nose, and use tools like a pop filter or windscreen to reduce unwanted noises while you speak.
Make sure that Gamecaster actually detects your microphone. Check that Windows can see your microphone in the Sounds options, then in Gamecaster, check to see that audio is being detected in the audio mixer.
Once you're all set, you can click on the cog icon to open up Gamecaster's microphone options to dial in your microphone audio perfectly.
The volume meter is the first and biggest factor in your microphone's output. Lower it if you're coming in too loud, or give it a boost if your voice is a bit weak.
You have the option to set different audio settings per scene. Enable the Per-Scene Audio option if you want to have different settings (e.g., having your microphone on mute in a BRB scene so you won't forget) on each of your setups.
Noise Suppression helps keep background noise down, but like the tip above, it doesn't replace an actual quiet environment.
Gain is an instant boost to your microphone output if it's still a bit weak. Careful that you're not actually getting too loud that your voice is maxing out people's headphones and speakers!
Some webcams and capture cards don't transmit video in real time, and your audio may not be synced to your video during the stream. Delay gives a bit of a buffer to your voice so the video has time to catch up.
Convert To Mono may help if your microphone output isn't working correctly in stereo or only outputting through one ear.
Input Sensitivity or Noise Gate gives your microphone voice activation depending on the threshold you set. Among all the options this will take some tweaking to get exactly right!
Turning on the Compressor lets you set a threshold level where your voice volume automatically gets lowered if it tries to go above it. If you expect to be reacting with a lot of shouts and loud noises on your stream, turn this on so you don't deafen your viewers!