toploaders: Semi rigids are popular for sending in cards to get graded but dont provide much protection, so use the rigid toploaders for regular sales, but be aware that if you use them in regular PWE (plain white envelope) sales without paying extra to mark it non-machinable, the toploader can get mangled in the automatic envelope sorters
Muldrotha, the Gravetide Among the most powerful graveyard-based commanders, Muldrotha, the Gravetide turns the graveyard into an extension of your hand
Custom card tournaments are a great opportunity for you to pit your creations against others
This completely depends on your priorities
1 card of any rarity is Traditional Foil
Floodborn characters are much more powerful versions of characters, affected by the flood of ink that happened in Rise of the Floodborn in some way