Condenser or dynamic? Cardioid or omnidirectional? USB or XLR connectivity? What to look for when choosing a microphone for podcast recording?
The room and acoustics
I start with acoustics because this seems to be one of the problems, I hear a lot. People get a large-diaphragm studio microphone and hope that the quality of their podcasts will improve drastically. The reality is that it might be worse than with your 10 EUR karaoke mic. The problem lies in the room and the pickup characteristics of the microphone. If you have a very reverberant room and a good condenser studio microphone then the microphone will pick up all the acoustical characteristics of the room and the result will be a distant-sounding, washed-out voice. If you have a good sounding room (for a podcast it should be quite a dead room with minimum reverberation) then a regular studio vocal microphone will be particularly good because what makes them a bad choice in a bad sounding room is also their strength in a good sounding room; the high sensitivity of the capsule makes them less sensitive to your movements behind the microphone and the result will be more even and polished from the get-go. In a reverberant room you would need a microphone that picks up signal mainly closer to the capsule and not so much from the other side of the room. In this situation a dynamic microphone is preferable. A large-diaphragm dynamic microphone that is also named something referring to podcasts, like a Pod mic, is as safe as you can get when talking about the pickup characteristics of the microphone.
Microphones that are designed for podcasts usually also have a shock mount and some form of windscreen already built-in, so you will not need to buy them as extra accessories. The shock mount eliminates the low rumble that might bleed into the microphone from the street as well as reduce the pickup of footsteps in the room or tapping of the feet. The windscreen keeps the recorded signal clean from sudden bursts of air when you speak into the microphone.
Pickup Pattern and Multiple Participants
Keep away from omnidirectional microphones if you do not know what you are doing. You want to be able to point the microphone to the source and avoid everything else as much as possible. Cardioid is what you need in most cases. Omnidirectional or even figure-eight pickup pattern microphones will work if you wish to pick up people around the room with a single microphone but even then, multiple cardioid microphones would be preferable since you would need a good sounding room and take into consideration how far people are from the microphone in relation to how loud they speak. To get high-quality end results it is way easier to have a multiple microphone setup. You would need an audio interface with enough microphone inputs and a microphone for every speaker or at minimum one for two speakers.
The Connection
USB, XLR, TRS, TTRS, Bluetooth? All of them would work if your signal receiving end accepts it. The proper signal path would be with an XLR connection but microphones with an XLR connection also need a preamplifier. For podcast recording a 100 EUR audio interface would be perfectly fine, containing a preamplifier and a USB connection to the computer.
For spoken words however a separate preamplifier is not necessarily needed to get high-quality results. With a USB microphone you can connect the mic straight to the computer and it will work fine. A separate preamplifier is needed more when you record singing because vocals can be extremely dynamic, and you would most probably clip a USB microphone sooner or later. Spoken words are a lot more static, volume-wise.
TRS or mini jack with three connection lanes is for smartphones, right? Wrong! If a modern phone has a jack connection at all then it is a TTRS that has four connection lanes, meant for stereo signal one way and a mono mic signal the other way. Although If possible, I would avoid anything that needs to be connected with a mini jack. If you need a microphone to connect with a smartphone or tablet, then get a lighting or USB model. Or a class-compliant USB audio interface and a microphone with an XLR connector. The separate audio interface for a mobile setup of course is not very convenient and there is also the issue of powering the devices that need to be thought about. So, for a mobile device I would go with a compatible lighting or USB microphone.
Conclusion
Strictly for a microphone go with a cardioid, large-diaphragm dynamic one, it will give you decent quality in most environments. The connection really does not matter, just make sure your devices are compatible with each other.