***This is more clarification for those with a turbo controller***
After trying to understand the game and methods that others tried to share using the turbo controller, I was still left confused. So I'm hoping to shed some light on it for those that are In my situation.
This game is divided into two sections.
Arcade mode (Top option, in red title). This is where you would use your turbo controller. You will NOT earn cash to buy the weapon cards, but they are given RANDOMLY after every match. So plug in a turbo controller and let it run overnight (I did mine for 2 nights). I have a Hori EX2 and turbo ed A + B on the middle speed settings and left stick angled down-right with a shoe. This would loop the game with earning quick deaths, earning cards, and starting up again. Check before leaving on overnight to make sure you don't get stuck on the leader board save section after the game over screen. If you do, adjust your button speed setting. If it bypasses the screen the first time, you are good to let it run for as long as you'd like. You will NOT earn all cards this way. I was still left with about 8-12 cards that I used the other methods for earning cash to buy the rest.
G-Mode (Blue title 2nd option)
I needed about 20k credits for all weapon cards after turboing. On normal I completed the first level with S Rank until I had the funds.
You buy weapons on the 3rd option on main menu (1st purple texted option). Select the character you are working on. The weapons you were given are greyed out and unable to purchase. Some are locked due to not owning the level 1 of that particular weapon card. Achievement will unlock when owning all weapons for one character
Good luck, and ask if you need anymore info.