Discounting activated abilities of of lands you control by 1 is pretty significant and makes cards like Nykthos, Shrine to Nyx (currently ruining lives in Pioneer in a mono-green deck, coincidentally) and Cabal Coffers that much easier to abuse
Guac & Marshmallow Pizza doesn't seem to give much to the combo versions, but the untap might spawn a different variant that could have some mana dorks - or enables a new combo altogether
Dragon Shield will be your favourite brand if you dont mind a bland design but appreciate the high-quality sleeves that wont break the bank
But since it's so cheap and has the potential to fuel any discard strategies as the game evolves, it can be a powerhouse in time
Commander is a huge format
Even out of the box though, Bellos deck is very cute and pretty powerful, so that might be worth the price of entry alone