Commander, also known as EDH (short for Elder Dragon Highlanderthe original name of the format), is known for being more casual and enjoyable than some of the more intense formats, like modern or legacy
The rest of the options either make mana for a Limited purpose (Like Beastcaller Savant whose mana can only be used for creatures) or something like Servant of the Conduit that turns energy into any mana
Starmie is the evolution of Staryu and it has an attack powerful enough to bring us one step closer to putting the practice duel out of its misery (I mean, of course, winning the very informative practice duel)
Ardyn Izunia Varragoth, Bloodsky Sire is a solid creature with deathtouch, decent stats, and a repeatable tutor
I've always eyed Lotus Cobra, but every time I think about buying one I remember I have a fetch based cube, which means it accellerates to five mana on turn 3, and that's way ahead of the four mana you can ramp up to with every other ramp spell in my cube