Oops sorry I was posting to somewhere else... Had something else written in here for you, goes to show to many windows open at once not good.
What I was going to say is that there is a site that I've been using to buy currencies. Not sure if there is a place you can just get USD into the system and then get it transferred to this place to buy into XRP. Like using Coinbase for instance and buying Eth and transferring it to a different service to buy/exchange. I know I've tried to sign up with other sites and im going on months without getting "authenticated". Least Coinbase was quick and easy about it, and I think soon they should be adding XRP actually to their market place.
I use Cryptonator. The downside is that getting USD into/out of it is nearly impossible to do easy right now (mostly Euro site), and prices tend to be a little lower than most market levels but that keeps the "value" at least a little stable. Its not as volatile with the ups and downs in the market. But if you use something like one of the other sites or potentially Coinbase to actually just get your funds in the system it might be good. Take a look at it, setting up accounts was still quick last I checked 2 weeks ago (just took minutes) as I helped a relative out.