I'd recommend using resources like TCGPlayer to find the market average, and then try to find listings below that, so you're at least paying cheaper than you might be
These guides can be a helpful starting point
I think the fact that Inquisition of Kozilek is more limited in scope this way definitely makes the card more interesting, but its universal enough that it helps alleviate Moderns historical issues around having too many narrow disruptions spells
Sanar Goblin, he/him Sanar doesn't care much about finishing his creative projects, preferring to flit between half-finished designs as inspirations strikes him
Enduring Ideal - At 7 mana, Enduring Ideal is challenging to cast, but among all the Epic cards, its effect is most likely to win you the game
What Lady does is help you refuel on cards so you dont run out of gas too quickly, and hopefully give the much needed push to end the game