the farm is a place where you store digimon and many other functions. the digivice have four functions, that is first is feeding. Feed digimon to increase their level and highly recommended to harvest meat every 30 minutes or an hour to speed up you level in the game. Next is training training is not really important because you can increase level by feeding meat but it can increase luck. The third one is digivolution you will some digivolution item for starters. to evolve to champion level digimon you will need a very basic two element but to evolve to ultimate there is a element event each day with different element everyday. For megas you will need a digimon Descend and cant randomly digivolve to mega's you must beat the mega's several times to become one. The last function is digimon set-up team a group of 3 digimon in a team and you can sort digimon teams by 3 group based on your preferences.
Thing you need to buy
the first one is the the place your grow your meat and this the most important in game and the restaurant that is the building with white roof that increase your stamina. be sure to keep upgrading after it was finished. a quick tips; dont click the stamina building after it was finished and make sure your stamina is empty and then click it then your stamina will be full then upgrade it again.
the building with purple roof is a place to store meats so that you can keep more meat for future use.
the building with the light blue roof is the dojo a place where you can get a random resistance by sacrificing same element digimon.
luck is very important in this game. try to increase luck by training or consuming digimon. best do this in rookie because the luck might not increase and it will be frustrating if it does not work in champion and ultimate level.
you can check the evolution chart in the link below. The list is from digimon cyber sleuth but this is almost accurate because the game itself is from cyber sleuth that have been altered some how
for more please leave a comment and see what i can help