Remember, some of the more specific ones may be better for your decks specific theme, even if they arent as generally good
For example, there are enough copies of Gaddock Teeg around now thanks to Ultimate Masters that the price of that card has dropped from $50 to $7
Try a Ruby Medallion to keep your red spells cheap, and use Koth, Fire of Resistance to dig up Mountains and keep the spells coming
The green ability is aggressive and creature focused, the white ability provides an answer for a potential problem, and the blue gives you a tool that helps with tempo and can temporarily answer threats
1 Isshin, Two Heavens as One
With the amount of savings on the line, this makes a lot of sense