Each character in Soulcalibur VI has a fairly overwhelming amount of moves, so one of the first things you should do is get familiar with their most important ones. While in training mode, pull up your Move List and focus on your character's Main Attacks to start. You can select any move with the X or A button to see it in action; that will give you a good idea of the speed and range of every main attack.
Once you're comfortable with your character's key moves, you should continue this process with the rest of your move list to get a better sense of what your favorite fighter is capable of. Then, mess with these moves yourself in training mode, trying to build up an arsenal of attacks that include highs, mids and lows, close-range and long-range moves, and moves that can start a basic combo.