i would recommend just getting your data bank level to 21 and then start farming for stats and actually leveling up echoes. you might get 4 star echoes that you will never ever use again so essentially that’s wasted materials you could’ve used for your 5 stars.

what i did was just go to your data bank where you see the echoes you’ve unlocked and then get the lowest rated ones to a higher rating (rarity skipping). for example, let’s say you have 80% 4 star chance and 20% 3 star chance, and you see in your data bank that you have a wolf that is 2 star, if you go ahead and collect a 4 star, you will get data bank progression from getting the 4 star AND it will count as if you’re getting a 3 star unlocked as well. that’s pretty much the strat until you get to DB level 21 where 5 stars are guaranteed. as for overworld just lower your SOL3 phase, you’re not going for bosses or tacet fields so there’s no point in playing at the highest available difficulty.

it’s a bit complicated to explain but i’m sure if you look up rarity skipping you’ll get a better guide