If you're finding it difficult putting a significant combo together early in the game, never fear!! I had just about given up hope of ever getting anywhere near a 100 combo, when along came the boss fight on Act 2 chapter 8. With my meagre skills I was able to easily reach 100. Here's how -
The game will lurch back and forth from normal vision to hell mode, but don't forget, you can visit hell voluntarily. So, when the battle begins, go to hell. It makes it easier to fight the boss. Next up, use a combo that ends with a stun and use twin swords. You should also have your twin sword mastery by this point. I used the combo x, x, y, y, b. I just mashed it over and over and over again. The boss will then do a compulsary hell mode and divide into a blue and an orange form as well as his own hell form. Pick one of the coloured ones and focus your combo of choice on it until it dies and then move to the next coloured doppleganger. Repeat the dose. Once the coloured baddies are gone, get stuck into the main man. If you keep getting your stun attack in he won't have a comback. The game then automatically switches you back to normality, but don't stay here. Go straight back into hell and simply repeat the steps above. It's an easy 100 combo I tells ya.
Good luck!