Hello
Most robots today use a microcontroller, as this makes it very easy to add some intelligence to your robot. So what is your experience with microcontrollers so far?
If not much, don't worry, getting started with microcontrollers is not that difficult, the easiest way probably is if you use some development board which comes with tutorials.
As your main goal is to start with robotics, I suggest to look for a development board which have all the basics on board to get you started with your robot, e.g. motordriver, some leds/lcd display, analog inputs for sensors...
A board that contain all these and also other stuff, and is still compact (so you can easily fit it on your robot) is the **broken link removed**. It comes also with step-by-step tutorials.
You will also have to think of some sensors you want to use with your robot for obstacle avoidance, line following sensor, ... Some basic sensors that you will need if you want to build a mobile robot are summarized **broken link removed**.
Hope this helps.