MY PERSONAL OPINION
I would strongly recommend getting a rainbow 3* 3.50 and a rainbow 4* 3.60 team first. For some relevant links ( linky, linky )
Grimm 4* 3.60 is better in your current situation. Grimm 4* 4.70 tends to be the most versatile of the Ramming Pulverizer trio.
Scarlett works well with two healers & Wu Kong