Marvel Future Fight fan and Alliance site
Cycnicalex is one of the most popular MFF streamers, most people would count his guides a the META. Very useful spread sheet even.
This site has a nicely laid out UI that shows you what characters are worth the effort and what ones are not, this also has a Uniform info graph which shows you what you need to upgrade, what uniforms it's linked to and what uniforms link to it for special bonuses.
A illustrated guide on how to build characters, rotations ctps etc etc
Calculate the amount of BAM you need, click file the select "make a copy".