I agree with Mike, it’s pretty hard to gauge where you could take it, to know if we put you on a good path or not. And it’s better that you make sure you set your first project goals wide enough to know you don’t paint yourself into a corner.
But here’s a couple of things to think about. You mention you want to use servos - these use PWM outputs. This is a pretty common feature so you can use pretty much any device, then you need a few breakout boards or extenders (or even the G-plugs, they’re quite neat) and a mainboard, of which I think the Cerberus is a pretty good value starter device. And the Cerberus has a tinker kit that is also a great way to get a few common modules that can get you started, or you can just buy the Cerberus mainboard for $30.
If you want to use RC (brushless) motors, then you continue to use PWM outputs to control the speed controller, but if you want to use other types of DC motors then you really need to select a suitable controller board that sits between the mainboard and the motor.