You have to check first if your general's troop type complies with the faction you are currently using (temple/church) and to what level your troop type training skill is currently at (example is temple's skill Oriental Horsemanship for light cavalry atk and def bonuses). If you go to Generals then Roster, you would be able to see a troop type name on the right of a certain general row. Click/tap on that icon to check the troop tier. Temple faction troops are on the left side and church faction troops are on the right.
Another one is leveling certain lab skills that would benefit your generals in relation to attack, damage, damage reduction, defense, etc...
Third would be upgrading your current equips as well as leveling the blacksmith. A good weapon to farm for would be the hunting event dungeon as the last 2 stages can be cleared with those aforementioned atk/def of your generals. The Takenomata Kaneko has an initial atk of 250 and the bonus atk per upgrade is like that of a level 45-50 weapon.
Fourth would be the generals in your army. Do they have skills that only work on a certain troop type? Do they have synergy with other generals? Would there be inherited skills from other generals? Do they have proc/triggered skills? Do they have passive skills like atk/def bonuses or troop regen?
Fifth is the formation of your army. For starters Python is the mostly used because of the atk bonus. But if you are the "kill or be killed" type of player then go for crane for speed - if and only if you think your army already had decent atk and def ratings.
XD