Our first bit of advice is to learn to love audio. Doing so will help you to advance the overall quality of your video in ways great cinematography can’t.
That said, Lavaliers and Shotguns are generally the best for video. If you can only buy one mic, we recommend a shotgun mic with a boom pole and shock mount. This setup is highly versatile and mobile. The only downside is you have to get someone to hold it for you.
Wireless lavaliers are also great mics, but they can only be on one person at a time. However, once attached, they practically go into “set it and forget it” mode. That is, as long as you’re monitoring your sound for anomalies, like static, peaking or rustling clothing; you and your talent don’t really have to worry about them.