Possible Improvements (in order of cost):
0 CMC
Canopy Vista: ~$1.80 each
Temple of Plenty: ~$2.10 each
Scattered Groves: ~$2.35 each
Sunpetal Grove: ~$2.35 each
1 CMC
Oppressive Rays: ~$0.15 each
Myth Realized: ~$0.40 each
2 CMC
Search for Azcanta: ~$11.50 each
3 CMC
Boon Satyr: ~$0.30 each
Stasis Snare: ~$0.50 each
Ardent Plea: ~$1.25 each
Detention Sphere: ~$1.55 each
Story Circle: ~$1.80 each
Bow of Nylea: ~$1.85 each
Courser of Kruphix: ~$4.35 each
4 CMC
Frozen Aether: ~$1.20 each
Cast Out: ~$1.55 each