I seem to do alright against kredders just by waiting the four hours between tournaments. I just keep my weapons nice (tournaments), and choose a specialty and dont focus on anything else. I did four slots for relics at by level 15 so I like to have a big team. I also spend the majority of my kred on two main characters because generally if I keep a sea of whitebelts then a single blackbelt will slaughter them all. That being the case I use percentage style relics rather than raw number relics because those have an amplified effect against white belts. I chose to specialize in heavy weapons, so I stack power and crit chance on relics instead of attack speed. This choice helps all my characters because they all use slow weapons.
Just stop treating the game like a sandbox and it’s not as difficult as youre making it, although I’m sure this problem will grow exponentially as I level.