I have 4 brushes (all of which I got for pretty good prices).
For enamels I use a Badger 200 and a Badger 200 fine. They are both single action bottom feed, internal mix. I like both of them. I use the 200 for general painting and the fine for detail or getting into tight spaces painting.
I use a badger 350-9 spray gun for future, I think I found it on amazon for $10-$20. It's external mix bottom feed. I wouldn't use it for paint personally, but for large areas or misting it works well.
I have a Paasche H I use for acrylics. This is probably the nicest brush I have and it came with ehavy, medium, and fine needles. It is also external mix bottom feed, but comes with a color cup for top feed.
I have experienced that the external mix brushes are a LOT easier and quicker to clean. I have also had the color jar get a little loose, though not fall out, on the external mix ones (but not the internal mix even though they are all bottom feed).
Of note, I don't think I paid above $100 for any of them, but I was able to take advantage of sales. I think I found the best prices at either amazon or chicago airbrush.
I will fully claim that I am NOT up for a double action airbrush at this point, so I haven't branched out in that direction. I think they are a little pricier, and I'll probably experiment in that direction someday, but I'm not there yet. I find a single action forces patience and a deliberate approach on me.
Groot