UK and Aussie citizen going to the Virgin Islands and Costa Rica

hey everyone!

Im visiting a friend in the US virgin islands and also Costa Rica, Im currently in canada on a 2 year WHP visa and going through the states. Im going to the virgin islands and also costa rica and was wondering about the need for return flights and visas etc.

I was wondering if I flew into the british virgin islands if that would be easier in regard to visas etc. There are ferries to the US virgin islands. The reason Im asking is I want to keep flexible on when I leave so would like to see if I can just book a one way ticket, though i will book a cheap ticket back into canada just to avoid hassle at the US immigration. thanks!

any information on getting between the islands and costa rica would also be helpful. also i my friend said id need a return ticket out of costa? thanks!