1. The Main HUD
This part holds mostly your character's status aswell as hotkeys. Any status ailments that are inflicted are displayed next to your level.
The center section holds hotkeys that you can map by using the menu. Simply open the menu and highlight the appropriate item/skill, then press the corresponding hotkey. For skills, you may only map buffs which have at least 1 skill point attached to them.
The green bar represents health.
The yellow bar represents experience.
2. The AP Bar
Shaped like the original sword that I had created for this hero, the AP bar represents a sort of "cool down" period for combo finishers. As long as you have AP, you can use your combo finishers, but once it runs out, you are limited with 2 attacks.
3. Combos!
This part of the HUD simply shows the number of attacks you have landed on enemies. Higher numbers provide a small strength boost (with beatdown enabled) :]
The rest should be easy enough to understand. (Shop / Menu screen)