These kinds of interactions are essential because giving out all those resources can come back to bite you if you don't protect against it
The most efficient of these new Hydra-like creatures is Mawloc, who fights opponent creatures when they enter the battlefield, and even comes at a base 2/2 before paying any X costs
One card in particular that I think could use another look is Patron of the Moon: (EDHREC Rank: #620) While the card is expensive, its Moonfolk offering ability allows you to discount the mana cost by sacrificing a Moonfolk, and you can cast it an instant speed
Let's say I'm building a Ruric Thar deck
Now this is where decision-making and tactics come in as you have to balance resources in your hand, cards, and mana necessary for your strategy
There are some clear, high-value cards you might have heard of Mana Reflection, Dryad of the Ilysian Grove, and Dark Depths