I personally train with bronze arrows, but that's because I'm cheap. I would probably use iron arrows between those, but if you were to want to spend the bit of extra money, I'd get mith just because it's only 5k more if you buy 1k of them (which is not very many for training).
I'd say attack first, since it's lower. Thanks for the re-assurance as that's what I did. But I also got 71 strength due to the strenght doors, so I'm going to get 70 attack, 75 strength and whatever hp that brings me out to (should be 88 combat according to the tip.it calculator).