Generally speaking, in decks that are three or more colors, you want to play almost all dual lands, along with enough basic lands to support whatever ramp is in your deck (Land Tax, Kodama's Reach, Rampant Growth, et al.)
Art preference aside, Erika and Venusaur are usually popular inclusions in vintage and modern sets alike, so it's clear why their combination results in such a high price
Unlike the normal cycling ability, basic landcycling doesn't allow you to draw a card
Dimir is solid colors to manipulate the top of your deck, either through scrying or surveilling
If they have a Don to use on their defensive turn, make sure to attack with your strongest Character first to present more of a threat and not have it rested by Leader Bonney
Soulburner is built around a reincarnation strategy, meaning that you send your monsters to the Graveyard in order to summon another copy