There are a few of us on this forum that show Arabians in dressage.
Where I board my horses, we now have a collection of DIY Arabian/Amateur owners. The general consensus is that they are all pretty amateur friendly horses. We’re just doing the thing with lessons and the occasional clinic.
Another local friend of mine went PSG on a little self-trained purebred. They have a lot of grit and heart. Same friend now has a Hispano-Arabe that she’s showing, except he’s a lot trickier to ride and is a lot more unpredictable. Our horses range all over in terms of blood lines, but all receive pretty dang good comments in terms of gaits and quality and have regional/national titles.
But if you like a smart, sensitive horse, then you may be able to find the fit for you, especially if you ignore any kind of looking or spooking. I don’t think of my local group of friends, any of us paid more than $3k for our horses since we were all younger/broke amateurs.
In terms of breeding, I don’t really see such a hard and fast rule anymore. There’s bloodlines I personally don’t jive with in personality, but looking at Arabian sport horse nationals, there were a number of horses at FEI that have ‘halter’ or even ‘western pleasure’ bloodlines. Just look at the quality of the canter and the tension and I would make a decision that way.
I was just impressed that my coach has really enjoyed coming to the Arabian shows to coach us. At least in our area, there’s a very different vibe than many of the open dressage events in terms of being pretty amateur friendly. I could always find someone to help leg me up or everyone is cheering for each other/etc.
I like that I have the option to do both Arabian and open dressage events. Many of the Arabian events are more affordable in my area too.