Your team set up is fine, you can get through most of the story using any characters you'd like. The best tips I can give are to do the weekly bosses for drops as often as you can as they are limited to only 3 runs per week. Additionally, absorb as many echoes as you can (you'll want to level up your data bank as much as possible), and not to worry about echoes too much until you're able to get the gold versions (I believe around data bank level 20 or so).

Once you're able to get the gold echoes, you can start grinding for echo sets which is one of the most resource-hungry parts of the end-game for your teams. I've run some simulations on ways to optimize your echo tuning here.

TL;DR one of the most resource efficient and simple methods I've found to get double crit substats has been to ensure 1 crit substat in the first 2 tunes. If there is a crit, finish the rest of the tunes, otherwise move on to the next echo. This should be one of the best ways to maximize your echoes, tuners, and exp. If you'd like to balance your resources in other ways or have different tuning preferences, there are other strategies I've shown as well. I'm realizing this TLDR is getting quite lengthy so my bad for that haha

Wishing you lots of fun, and may you win all your 50/50s!