Hi Hadess. Thank you for the kind words, I'm glad you're enjoying the game! If you want to create your own character card I tend to try not to go above 8 with any of the stats as this means the character has to roll at least one dice to succeed in a check and can't just auto succeed (with a small scale for failure.)
For pool I try not to go above 9 dice and stick around 7, 5 being the lowest. The Philanthropist is an exception with a pool of 10 as they have terrible stats and make up for this by 'paying their way' through stat checks.
In terms of skills do whatever feels right for the class. Create something interesting and out of the box that puts the game on its head. The Tulpamancer for example or the Artists homunculus.
It's best to think of a very interesting skill, then make it weaker and have your initial idea as the advanced version.
Good luck and good investigations!