So here's a trick that'll guarantee you a gold card out of the 30,000 coin Kard Pack, it is pretty lame and very time consuming but still faster than trying to get 150 souls for the Kombat Pack.
It is a very simple method and works for a lot of other iOS games as well, what you do is you backup your save, open the Kard Pack, if you dont get the card you want you reload the save. Keep doing this until you get what you want. Worked for Injustice Mobile as well. Do this at your own risk!
Step by step:
1. Download iFunbox (or similar) program that'll let you access the files on your phone.
2. Set your iPhone/iPad on airplane mode (you could try without this step but I did it just in case).
3. In iFunbox go to User Applications > Mortal Kombat X and copy the "Documents" and "Library" folders to your PC/Mac.
4. On your device buy a Kard Pack in MKX, if you don't get a gold card, double tap the Home Button and close the MKX application.
5. In iFunbox refresh the Mortal Kombat X directory, click and drag over ALL the files and folders in the Mortal Kombat X directory and click Delete, it will only delete some of the files.
6. Drag and drop both the "Documents" and "Library" files from your backup folder back into the device.
7. Start MKX on your device, open a Kard Pack and repeat.
Once you get what you want, keep the MKX app open in the background as you turn airplane mode back off. I had some trouble where my progress would disappear when I had the MKX app closed while turning airplane mode back off.
If you have any questions, ask away.