If you are getting card advantage out of discard effects then Hymn is the best of those because it costs you the least tempo
There are plenty of different game options to choose from, like tag mode (which lets you control two players instead of just one) and juice mode (which turns the game speed up to crazy levels)
These are the ones most often slipped into cheap vintage lots or sketchy booster packs
however, only 10 PSA certified copies are known, a very important note because there are many counterfeit copies
Fun Ranking: Want to Build Rendmaw, Creaking Nest This is the alternative Golgari precon commander, and it seems pretty fun
In a GB Constrictor shell, it may even be possible to remove the energy theme completely and go for more cards that can get +1/+1 counters, or include Heart of Kiran together with Karn