Howdy and welcome to the bench!
Flat-ringed boards should yield the safest bows, but try to find a board with the least amount of grain run off as possible and go for it. I am currently making a youth bow from a bias ringed red oak board, so we'll see how it turns out, I'm just about to start tillering. Some of the vets here can probably tell you much more, but I say find the best board you can and start working, you'll learn a lot from the first bows you make.
Hickory is great bow wood, very strong in tension and I have read that hickory board bows even with violations are ok, especially at lower draw weights, so edge or bias ringed boards may be ok. But Personally I would still try for flat ringed or a board with as few runoffs as possible.