Been running all the races through to the first city to get all the racial cards. I also clear the dream dungeon each run for the first time bonus pack to try to get all the parts for a dream deck to use in arena. Have the dream deck built now with all equipment except I'm still short 1 enter the dream. Looking forward to trying it once it's complete.
Some of the decks I've been using to power through early campaign for farming on a budget are:
Human, Orc, Dwarf: Warrior -- pure red orc agro deck, fast games that can win by turn 4-5 on average although I find that if I stall out a turn or two early, these decks struggle to catch back up.
Coyotle, Elf, Shinhare: Cleric -- green plant based using briar legion, briar patch, vine trap (with gloves), and bramble creeper. I splash red/blue/blood depending which race I'm running since green doesn't have much removal on it's own. This deck is a little slow in the early turns, but once I start to play a few briar legions, it's a win.
Necrotic, Vennen: Warrior -- pure blood orc agro. Similar to the red version, but this time using the blood orcs. Blood agro is a little more consistent than the red version since it has a lot of life drain so you aren't on a clock to win before turn 6'ish.