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
Gardevoir ex Notes: All the damage that Gardevoir ex sustains can be sent to the opponents side via Munkidoris Ability of Adrena-Brain
This can be an incredibly fun deck by abusing cards like frantic search to effectively draw 4 and potentially discard none, but can be hamstringed hard by cards like drannith magistrate
This time, they put the Coastal Piracy effect on a 6/6 trample vehicle that can draw you cards, with a little help
Arcana Force VI - The Lovers was first released in the set Light of Destruction: Special Edition, illustrated by Konami
Eternal Chaos Target 1 face-up monster your opponent controls