When I was younger the first good transformer that opened up more operating possibilities was the MRC Dual Control model. This unit has 2 cab controls in one housing making running 2 trains fairly easy out of the box. I think it's a decent price for what you get, and they last forever. I have a similar model from my N gauge stuff and it has to be 15 years old at this point, still like new. It's also a good opportunity to move away from the 'train-set' type of hobby controller which aren't nearly as reliable or durable.
Even with that, and an older train controller, you could have 2 mainline trains running and use the older controller for yard switching, for a total of 3 blocks / trains - that would keep you busy for a while! This unit will easily power accessories like the switches and other items like lighting.