I take portraits at home, so this is probably the most basic setup but it may not apply outdoors. I use two manual flashes, one is triggered by the camera via a basic wireless trigger (mine are lightpix) and the second optically from the first. It's the most affordable setup except for having a pc sync cable run from the camera to a flash, I've tried it but it's a bit cumbersome. Especially if you use flash in a "studio" setting where the background is less important, I'd suggest you experiment with a zoom you may already have before getting a dedicated lens. Also consider a budget for light modifiers, they make a significant positive difference, even simple umbrellas. Manual flash made me learn how to dial in the light balance, you may achieve the same with automatic exposure but for me it wasn't worth the extra cost (overall my setup is $200).
Originally posted by detlef how many triggers are needed
I've learned first to use one flash and then two
I think I would know how to use a third, but I don't have the space for it; I use a window as the third light source sometimes. Starting with everything at the same time can be daunting.