If I remember red maple was on the bad list of woods. Don’t quote me on it. I do believe that it was just the red maple variety that was bad but the others were okay. Since it’s hard for me to get my hands on maple that isn’t “red maple” I just stay away from it. Poplar is good. Not as expensive.
Your best route is to get willow sticks. Your buns will go through a ton of sticks in a short amount of time (at least in my case since I have three buns who are big chewers). So it saves a lot on money when you can get a bundle of willow since it is a cheaper wood to get a hold of.
If you are going to dry your own woods make sure that there are no pesticides that have been used near or on the tree that the wood is coming from.
I have a dehydrator that I use for drying herbs. I really like to use it for carrot tops since I have a hard time getting my hands on them. Dehydrating them keeps the tops around longer.