Wow, how demanding. 621061789.
Time for your team to carry me through the Lavender maps. :^)
I was trying to figure it out for a bit myself, no worries. I eventually managed to get each reroll down to about 4 minutes.
Rush the tutorial, do the premium gacha draw it forces you to, collect the gems for the guaranteed 5* draw and use them on another premium instead. After that you'll have 3 gems - do the first map and burn your 100 gold for another gem, and do another premium gacha. Rinse and repeat.