There are no "official" rules on how to do this but we recommend you do it in one of two ways.
1) ALL IN MODE- In this mode, you include all gladiators into the draft pool (with the exception of Champions and CF Gladiators). I would just do one or two of each of the basic types so you don't have 10 basic archers - 2 from each city - to draft from.
Tactics are handled a bit differently in this mode with only 1 of each tactic being made available in the draft.
2) ONE FOR ALL MODE- In this mode, you literally put in one of everything. That means, one basic archer is all you get, one basic attacker, etc.
Since these already exist in the Origins chips, it means you are only adding the City gladiators from TLC and RoR, and then the chips from your addon packs - which would be one Beastmaster and all Beasts from Beast and Master and 1 of each unit from LoTS.
Tactics are handled the same way. Only one of each.