Your opener

The first stage is played against monsters, and it hands you your first gold, units and item components. What you build from them has one job: win the first fights of stage 2, or lose them cheaply, since those fights start your streak.

Early shops are almost all cheap units: at level 3 a 1-cost fills 75% of every shop slot. Cheap units also have the most copies, 29 of each 1-cost, so a unit you hold two of, a pair, usually finds the copy that makes it a 2-star (3 copies). A 2-star is the biggest upgrade an early board can get, so buy pairs, and buy a second copy of a unit you hold over a first copy of one you might use later.

Play the strongest board you have, not the comp you hope to end on. Early fights are won by 2-stars and by units that share a trait, and those are rarely the units your comp finishes with. That is fine: they hold your health and your streak while the real comp comes together, and they go once it does.

The bench holds 9 units beside the board, and in stage 2 it fills fast. Keep pairs, units your items or early upgrades point to, and what is on your board. A single that fits none of these is gold standing still, so sell it: a 1-star unit sells back for what you paid, and selling one you might want later only costs the chance to find it again.

Between stages the carousel offers every player a champion holding an item, and players with less health pick first. Early on, the item is usually worth more than the unit: a component that fits many comps keeps them open, the way Slam or hold shows.