So I've just been using basic earbuds my whole life, never felt like spending big bucks on good headphones. Recently though, I've been really interested in what I've been hearing about IEMs. Youtubers and forum users have been name dropping a few of them, such as Moondrop Chu/Chu II, Salnotes Zero, etc. So I looked them up, and was shocked to find how cheap they are. They're like $20, in the same price range as the crappy earbuds I buy anyways! These kind of headphones seem like a whole world I know nothing about, with pros and cons I don't fully understand, so what would be the best recommendation for a first set?

I need and want to buy a portable AMP and DAC. I have no experiance in this, a beginner. I want to choose between Fiio Btr5 and Fiio KA3. I also don't want to deal with battery issue in long term but bluetooth portability feels more convenient.

Can't decide what should i buy. Any advice