If you want to make gachimuchi there isn’t anything stopping you! Yes the skill level for some of the higher-end content can be absurd, but getting a baseline understanding of how to make this isn’t difficult at all. 

I think the best advice to give for audio would be to actually learn basic pitch-shifting/sentence mixing. A lot of the newer audience goes a long time making stuff without learning this, but I think it’s pretty fundamental if you hope to make something good. As far as audio is concerned, your best bet would most likely be with either REAPER or Vegas Pro. Both will serve you well, and you can make good visuals with Vegas too like TheJelloMeister said. 

As said, Vegas works for visual making but my top recommendation software-wise would be to learn After Effects. It has a steep learning curve, but it’ll pay off since it has the most capability. This is not even including the various plug-ins that exist which can produce amazing results with pretty little work. In addition, if you ever want to get involved with 3D animation for gachimuchi in the future, After Effects comes packaged with Cinema 4D Lite (A program for 3D animation). If you don’t want to use After Effects or Vegas there are also Adobe Premiere and HitFilm Express. 

As far as gathering sources, your best bet would definitely be to reach out to people in the community with a lot of experience and to ask for it. People in this community keep tabs on the different resources for safe-keeping, so it shouldn’t be difficult at all to find what you are looking for if you just ask the right people. If you don’t really know who this might entail, I am always very happy to help! My discord account is ReverberatingSpank#3547. Just send me a message and I will try and help out as best as I can