If those abilities dont mention you choosing a Ring-bearer, they will go off even if you control no creatures, but if they do only trigger when that choice is made, you must have a creature to be your Ring-bearer for that trigger to occur
In general, looting a card back to the top of your deck is worse than discarding a card (since you can't take advantage of any graveyard synergies), which means the +1 is only powerful with a very narrow subset of cards (things like Miracles)
This ties very well with Dinas own ability, considering that this bigger creature can be sacrificed later for even greater value
Shell Get Her Revenge or Die Trying: A Love Letter to Gravecrawler I once made the outlandish claim on stream that I thought I had probably cast Gravecrawler more times than any other mage alive
That makes him a great early drop for the land-needy, while also giving you the body and presence that you are looking for
Trainer cards also give you the opportunity to synergize and combo effects with your Pokmon attacks and abilities, letting you get more done on your turn than your opponent