For the beginning,you need a flight simulator. There is few of them,and that choice depends on the PC you have,more precisely Microsoft Flight Simulators 2004 and FSX,X-Plane and P3D. They are all payware,so you have to think of that part as well. There is one freeware flight sim,but that is seriously bad,so I wont even bother to explain about it.
Then depending on the airline,you'll need some aircraft. Last one,is the ACARS client. That one also varies from one VA to another. Some have their own,custom clients. The ones that don't,mostly use some very old and badly unreliable clients
Other than that,you might need some add-ons to improve some aspects of your flight sim,but like I said,that's just possibility.
I'm actually the Owner/CEO of American Airways VA and while you are welcome to buy any payware aircraft you want, we don't require you to purchase aircraft to be part of the VA. IF all you have/want is freeware, I'm cool with that. Way I see it...life can be a complete B*TCH sometimes, so why make it more of one? lol
I'm a fairly laid-back guy. I try My best to work with My pilots, and I do offer certain rewards for those who are active (ranging from "monetary" bonuses to having an aircraft assigned to just them). We're actually based on en English (as in the county lol) site, and use their flight tracking software (which is very easy to use btw). Plus, I can supply you with all the freeware aircraft we use (though some of it is on here lol)
While I do mostly long-haul cargo, since that's what makes the VA the most $, I let My pilots decide what it is they wish to do.