Sung Joo’s Answer
From personal experience, there are so many great audio tools out there that it's becoming increasingly difficult to decide which ones to pick. Also, you have tools for different audio venues, such as Live Audio, Studio Mixing, Recording, Mastering, and so forth.
Depending on where your interest is, or even if you're just starting with audio, I suggest that you first pick your DAW (Digital Audio Workstation). I say this because many DAW softwares come pre-loaded with tons of audio tools that you can start using right away, such as EQ, compressor, delay, reverb, etc, with advance recording and editing capabilities. One thing to keep in mind is that each DAW is built for slightly different purposes, with many overlapping features. For example, audio engineers who are focused on recording and/or editing audio tend to prefer Pro Tools but you can easily record/edit audio in Logic Pro X or Cubase for example. Music producers and writers tend to love Logic Pro X but you can surely produce using Ableton Live or Pro Tools. I suggest that you try different demo versions, if available, and see which ones best suit your needs.
Of course, as suggested by Seth, if you need to record, you would need a microphone, a pre-amp, and an audio interface. If you're just starting out and want to keep your setup simple, there are USB microphones out there that combine all the 3 components for you.
Once you pick your DAW, and have the needed hardwares, try recording, editing, designing and playing around with the pre-loaded audio tools in your DAW. From there, you may find interest and/or require to do more than what the existing tools are providing you with. For example, I used Logic Pro X to record and mix a friend's vocals but I needed a more advanced tool to look into the audio frequencies and perform pitch corrections. When I searched online, I had found Melodyne, Antares and PitchMap. I read many reviews, tried all the demo versions, and eventually landed on Melodyne.
My point here is that audio tools should be acquired by need and purpose, depending on what type of audio projects you'd like to work on. DAWs will serve as a platform, in general, and you will most likely layer different audio tools on top of that. Below is a basic audio setup (of tools) that can get things started for you:
- Microphone + Preamp + Audio Interface (or just a USB Mic)
- Speakers or Earphones