Gameplay/Digifusion

Digifuse
Digifusion can be found in the upgrade menu in the Digimon Box.

Digifuse allows a Base Digimon to gain Experience (and thus increase its level) by fusing/sacrificing up to 5 Material Digimon at a time.

The Bit cost of Digifusion increases with the level of the base Digimon:

Digifusion Cost = Level of base Digimon * 100 * Number of material Digimon

The experience points (EXP) provided by the material Digimon varies by Digimon and increases with higher levels.

EXP gained = Combined Material Digimon value x Race bonus x Rarity bonus x Random Bonus

Digimon value = 100 x [base value (3 to 10 for most digimon) + level]

Race Bonus = 1 if no Material is of the Base Digimon's Race. 1.5 for one and +.1 for each additional Material Digimon with the same race as the Base up to 1.9 for all 5.

Rarity multiplier = 1 + .1 x Sum of Material Digimons' rarity (red stars)

Sometimes a Digimon will gain 1.5 or double the exp as a random chance event.

It is almost always worthwhile to fuse with 5 Material Digimon at a time as it grants all the Material Digimon with a higher multiplier. At least one should be the same race as the base.

Leveling Material Digimon tends to result in much less EXP than simply fusing them all to the base, but as digifusion can be fairly costly for high level Base Digimon, it can be a worthwhile measure to manage bit costs.

Non-Digimon Materials
There are other items in the Digimon box that are not Digimon, such as Floppy disks and fragments. Those tend to have very high base values compared to Digmon. However, they are all lvl 1 and of 1 star rarity. Floppies are all of the Dragon race, but others items can vary.

Floppy Disks

Bronze - 30 (so 3100 total value)

Silver - 60

Gold - 200

Digimon Evolution Items

Fragment - 40

Grain - 60

Crystal - ?