When Should I start #2.
I think you should wait a bit. There's no rush. Trainers are... *gasp* fun to fly! They may not be able to do some of the things other planes can, but then again other planes can't do some of the things trainers can.
Take your time. Once you've been at the field a bit, you'll get a feel for what kind of second plane you want. You'll also have a better idea of your talents for this hobby, and that'll help you make the best choice for you.