So I did some fusing, and this is what I found out. In order to get a card from level 1 straight to level 40, it takes 5 lvl 14 tabs. This can be achieved using the methods explained in the guide. Using only 4 lvl 14 tabs will bring you to 36. These results are assuming that the card you are leveling and the fusion material are both the same element (fire, water, wind). The type (demon, angel, mech, etc), however, was not the same.