ok lets say i ditch two of the little dragons from my hand for the effect to special summon the bigger ones. Do i get both of their effects to summon two of them? Because the only requirements are ditch this and one other dragon type monster so would the effects stack?
No, you can't double dip like that. You can't discard a monster that was already discarded to pay another monster's cost. You have to declare which dragon's effect you are activating and special summon the Appropriate Dragon Ruler monster.
You declare the activation of a mini Dragon and pay the cost. It's the resolution of that effect that Special Summons the respective "Dragon Ruler" from the Deck.
Their effects are not Trigger effects that trigger when a mini Dragon discarded. It's the same reason why you can't activate Exiled Force's effect when you Tribute it for a Tribute Summon or to pay Monster Gate's cost.