Keep in mind I'm a fairly new player.

1) Katie, Leanne, 2 archer (Bashira + another), 2 witches (Cloris + Calliope), 2 healer (Iris + another), Valerie. Focus on the units that allow you to farm Monday daily H, Phalanx 2 and Thursday daily H (in that order) - look up videos. Might want to CC an archer first though. Monday daily H will help with your gold issues and help with CCing other units.

2) Farm Pastoral Gate/Deep Forest Road and sell the units when you run out of gold.

3) Buy Box Expansion in the shop when you run out of slots.

4) See 1), add another mage and some duelists later on. Adjust team based on missions.