Well, I don’t know what bold cancelling is, but I can tell you that while training mode and mission will help you understand how combos can work, it won’t make you a more seasoned player. Often when players do training and missions, they may feel like they’ve got the knowledge and experience necessary to take on all comers, but the truth is it’s only one step. There is no substitute for experience.
If you are like me, when I first started out, I felt sorta the same way, but found that knowing fancy combos isn’t what wins battles. When you actually play a opponents online, that can add pressure and nervousness that may cause you to mistime and drop combos and links. The more you play though, you will learn and feel yourself open up as a player, relax, and your timing will get better. Practice a combo setup, and when you land it in online play, basically muscle memory should take over. Practice makes perfect, and experience can mean the difference between victory and defeat.
To tell you the truth though, the ranked battle system will often match you against someone much higher than your level most the time. So you are trying to merely get in decent experience, the other guys concentrating on running you over, which leaves you learning almost nothing. Stick to guys your level at first, and work up, it’s much less frustrating and more fun.
Also, know that your combos won’t help unless you find ways to land that first hit and get the combo going. That’s why setups for landing that first hit are just as important to know as a character’s combos. Make good use of your assists, mixup your opponent and confuse them, learn to read them slightly, and figure out what moves they use are punishable, and know your own characters as well. What can Morrigan use to land her first hit, what can you use your assists for, how can you confuse and mixup the opponent, etc. Dante has lots of good long combos that require some muscle memory to use but build lots of meter quick, and has good assists, Tron has some good juggles, big hitboxes, and her Gustaf Fire assist is invincible, and Morrigan has one hyper that creates a mirror clone to put pressure on the opponent from both sides of the screen for good chip and better combos.
There’s a lot of info to take in, but just practice and play at a steady pace, and you’ll get there. Also, try using the character specific sections of the forums to try and understand your characters’ potential.