The first bit I use in training is a french link. If you want to go to a very basic mild bit, its a good choice.
If money is no object then I love my Myler comfort snaffle.
Used to be, aound here there were only 3 types- straight, broken (snaffle) and curb. I started my horse in a straight bar (no chain, considered a straight snaffle) -- very simple. Never had a horse object to it. But we didn't ride with much contact, it was Off or On.