Get the largest throat space you can get.
Needle down feature is great to have.
For me a drop in bobbin is a must also.
I have 3 Brother machines. My first a basic beginner quilting machine for $129 that came with a walking foot and a table, the second is a lightweight for travel that cost $89, the third is a small embroidery machine with just a 4 in embroidery area. Wish I could afford a bigger embroidery but this one was under $300 so it will have to do for learning.
Later I bought a Viking Sapphire for $1100 that has a 10 inch throat and lots of bells and whistles. But my brother is still my backup machine if I ever have to put my Viking in the shop.