DJI Mic Mini wireless microphone kit, two transmitters and one receiver
The proper budget way into wireless mics for video: two tiny clip-on transmitters, one receiver, nearly two thousand reviews. This is the version without the charging case.
See it on AmazonIf you record talking-head video, interviews or anything with two people, a wireless mic kit is the single biggest upgrade you can make, and the DJI Mic Mini is the one most people end up recommending at the cheap end. Each transmitter weighs about 10g, clips or magnets onto clothing, and the receiver plugs into a camera or an Android phone.
What you get for the money: two noise-cancelling levels, automatic limiting so a shout doesn't distort, around 10 hours from a charge, and a quoted range of up to 400m in the open. If you already own a recent DJI Osmo camera the transmitters can connect straight to it without the receiver.
The catch is in the name of the listing. This is the 2 TX + 1 RX kit without the charging case. The case version costs more and gives you a way to charge and carry everything together. If you'll be out all day, that matters; if you mostly film at home, save the money.
Long-established listing with a large, mixed-star review history, which is what you want to see. Read a few of the critical ones before buying; the common complaint is about the app and firmware rather than the sound.
See it on Amazon