Jake's friend wants to get into music recording and is looking for a good USB microphone. Their budget is between $100 and $200. Leo says there's a lot of choices in that price range. Blue is best known for this category. The Blue Yeti is the top dog. He should avoid the Snowball, though. It has no headroom. Audio Technica's ATR2100 is very nice as well.
Carl wants to start up a podcast running four different XLR mics through a mixer. He wants multiple channels for each one. Is the mixer what he needs? Leo says that while condenser mics are more accurate and hear everything, he really wants a coiled diaphragm mic, which doesn't pick up everything - just the voice. Leo uses a Heil PR-40. But for a budget, the Shure SM58 mic is very forgiving. Leo says for a mixer, the Behringer XR18 is great. He can control it from an iPad, it has great mic pre-amps, and is simply a good choice.
Since the instructor is currently using a handheld mic, a better solution would be a wireless lavalier mic. The challenge here is that a lavalier mic picks up more ambient noise and there is a higher potential for feedback with the PA system. It will be important to make sure there's enough distance between the mic and the speakers to avoid this. A lot of companies make lavaliers, but here's a few to choose from: