It is strongly recommended that acquiring any hero with 5 stars at least in the beginning if you do not want to reroll a ton of times. Then you can go through Chapter 2 easily even in Auto mode.
Basically a character with more stars are more powerful than that with less stars. Although all the heroes can be awakened to 5 stars in the game, obtaining awakening materials is a bit tough. → Reroll tier list
What point in time is the best to connect to Nintendo account?
After you finish rerolling and get a hero you want.
How many F2P Orbs can be obtained?
It is widely known that about 190 Orbs can be obtained.
2. Battles
Complete Chapter 2
Once you finish Chapter 2, Training Tower is unlocked. It is a best place for players to get your allies to earn EXP to raise their level up.
Stamina
Max Stamina is 50 and the amount cannot be increased. Once you run out Stamina, play Arena Duels.
Can I turn off combat/support animations?
Yes you can. Tap the notepad/gear shaped icon at the bottom left corner of the screen and go to the settings menu.