The lastest Monopoly Go Fantastic Partners Event is Coming on July 29th, here is the Milestone Rewards for completing each level could be:

Level 1 (2,500)

Rolls x 200

Level 2 (6,000) 

Cash

Level 3 (13,000)

200-300 Rolls

Cash

Cash Boost x 10 minutes

Level 4 (26,500)

300-500 Rolls

1 x 2 Star 3 Stickers Pack

Mega Heist x 20 minutes

Level 5 (32,000)

400-600 Rolls

Cash

1 x Emoji

1 x 4 Star 4 Stickers Pack