I saw that login gift system on alot of games.
my idea: fortune wheel or scratch card daily one (choose 1/6). Requ: 2 gym badge completed on kanto.
Pokedollars, 5x ultra balls, 5x rare candies, rare held items, and with low chance jackpot some valuable rewards (3day ms, master ball, skin costumes, chlotes, hats)
And another idea:
New item to market
Silver pokemon fortune card for 5 coin, (contains normal rewards like pokedollar, ball, repel...and with 5% chance some valuable)
gold pokemon fortune card for 20 coin (contains middle grade rewards and with 20% some valuable)
diamond pokemon fortune card for 50 coin (contains the best valuable rewards and with 35% chance something super reward)