The whole Gladiator Beast archetype revolves around 1 strategy, battling, returning to the deck, then special summoning another gladiator beast. Gladiator Beasts special summoned by the effect of another Gladiator Beast will then gain additional effects. Go, Ojama! gives your opponent monsters that you can attack to activate your gladiator beast's effects.
Some Gladiator Beasts have effects to destroy cards on the field, but they usually have lower stats than your other Gladiator Beasts and need support from spell/trap cards to survive battles. Gladiator Beast Bestiari destroys a spell/trap card on the field when he is special summoned by the effect of a Gladiator Beast, while Gladiator Beast Murmillo destroys a face-up monster on the field. You can use anti magic arrows to prevent your opponent from activating set spell/traps and then special summon Gladiator Beast Bestiari to during the end of the battle phase to destroy it.
Surviving the battle is needed so that you can activate your Gladiator Beast's effect.
Half Shut allows your monster to survive any battle in exchange for halving it's attack this turn. Another option is halving your opponent's attack then having all your Gladiator Beasts attack that one monster, activating all their effects.
Mirror Wall almost always guarantees your monster to win when your opponent attacks it and has his attack points halved.
Use the first effect of Impenetrable Attack and select a Gladiator Beast you control, it cannot be destroyed by battle or card effects this turn. The second effect is less used but can be used to survive OTKs.
You don't need 3 Dimacari, but 3 Bestiari and 3 Laquari. But yeah, if you don't have a lot of trap / spell to keep them on the field, this deck is not that great. It's a budget deck if you consider only the monster, but it's expensive with the spell / trap.