i think early game ( constant g1 rifts , managing to get constant 20 pf streak ) should be focused on getting you 1v 3 characters invested . My personal focus was investing and building 12 beowulfs which get me easy 40 win streaks .
Some tips i could think of are:
1. looking into a couple of variants in your collections in which you feel comfrtable going 1v3 AND/WHILE longshooting ( i am biased , but beowulfs ).
2.thinking of a system in which you can have enough energy for your carries ( i personally start with my highest score beowulf -2xfights- move on to the next beowulf -2xfights- and so on , when i reach my last beowulf i have full energy for my first and i just repeat the process )
3. (your team fightscore +enemy team fight score )x multiplier x Bounty = your score
i will keep my highest score team (81.7k ) for X3 or higher bountys ( highest i got was around 1.4 mil score)
4. break down your streaks . first 10 fights can be autobattle . you will fight 20 times and then reset your streak in the 30s . Moments in which you wait for energy to push a higher streak are a waste of time if you have energy on other fighters *EDIT+ consider the bonus HP and ATK defenders get in high streaks , it might be worth to just reset to save time END EDIT*
5. have a exxp boost to give you some clear way of noticing small rewards ( a raised silver fighter , another lvl on ur diamond fighter etc ) and have some good music or something . Brace urself bassically for the grind .
good luck in the future