One of the important things about USING transistors is that most of the actual circuits are designed to minimize the effects of variations between transistors. In some sense, the standard topologies like "common emitter" are designed around "ideal" transistors, and/or behavior that is common to ALL transistors. Then you put a 'real' transistor in the circuit while being careful not to exceed its REAL limits, and everything should be basically OK. So you design an amplifier with a gain of 20, and pretty much any transistor with a "beta" (raw gain) of 40+ should work. Assuming max voltages, currents, frequencies, and so on are also within the specs of the transistor.