Once you start Combo Mode you will notice the combo bar appear and a green / yellow bar inside it will fly across to the right, what you need to do is press a magic or sword attack as it gets inside the 2 lines at the right side of the bar - if done correctly you will get a Bad, Good, or Excellent and it will fly across again and so you have to press a different sword or magic attack - if done wrong you will get a Miss! To always get 'Excellent' make sure you press an attack as it lands on the right line.
The more you combo the smaller the 2 lines will get until you get to the 11th combo, then it will stay the same size and its all about keeping your cool and trying not to slip up.
Know your cores:
As your adventuring through the levels you'll come across different types of core drops - Low Cores - Medium Cores - Upgrade Core (Highs) - Upgrade Core (Highest) and Force Cores. You can always tell if a core has dropped as it will make a 'bling' noise as it falls to the ground, a noise i love to hear
Cores basically add stats to your weapons and armors - low, med, high and highest upgrade cores add +'s to your equipment making them stronger or more defensive (stats go up to +7), whereas a force core adds a special attribute to slotted equipment like HP + 50.
Below is an explanation of each core so you know how to use them properly and not waste them.
Be careful when using cores on equipment which is +4 or higher,
if fail to upgrade to +6 your item will go back down to +3
if fail to upgrade to +7 your item will go back to Zero.
* Low Core:
Low cores are used for increasing stats on low grade equipment, they cannot be used on equipment like Titanium so if you want to practice using a core, practice with this one. Unequip your item your upgrading, right click on the Low Core and then left click on the item, if its successful it will tell you so and your item will now be +1.
* Medium Core:
Medium cores are used for increasing stats on Titanium or lower graded equipment and are used the same way as a Low Core.
* Upgrade Core High:
Red Cores are used for increasin stats on the high grade equipment and shouldnt be used on low grade weapon or armour. Osmium, Shadowtitanium etc, are what you need to be saving and using Red Cores on, anything else is waste. Just like Low and Med Cores, right click to use.