The third drop will be released later, so stay tuned for more information on these releases
A lot of balance and care goes into choosing the cost of a card, more than I can express here, but looking for similar effects on existing Magic cards can give you an idea of a fair costfor example, a ramp spell that puts two lands into play ought to cost 4 mana, per Explosive Vegetation
Loxi: I'm curious to see people run this as a commander, 3 mana lets this get rolling pretty early
14 Spellslinger/Storm As the name would entail, spellslinger decks are those that aim to cast and sling as many spells as possible over the course of a game of commander
A+ Tier / Bracket 4: cEDH These are the decks that contain all the raw power of the A+ tier decks but are just a little bit more meta-dependent
Helm of Chatzuk allows you to give banding to any creature for the low cost of one mana