I not only spent time researching what cards needed to get swapped in and out during certain matchups, based on other people's experiences with the deck, but I also made myself a quick-reference sheet that I could use the whole weekend to guide me on my sideboard process during matches
Example - some Uncommon cards were printed 4x on each Uncommon sheet, like Oasis
For a long time, it wasnt really possible to build a good Exava deck because there werent enough cards with her identity that did stuff with counters
We buy and sell a lot of bulk
Kagerokubushuu Kizaru / Shadow Six Samurai Kizaru Earth Warrior / Effect LV4 1900/1000 (1) When this card is Special Summoned: You can add 1 Six Samurai monster that does not share an Attribute with any monster you control from your Deck to your hand
In terms of upgrades, consider these: If your opponents rely heavily on their commander, try using Hinder and Spell Crumple Steal creatures with style