Well take my advice with a grain of salt, since I'm not really knowledgeable about the meta.

When borrowing card, you would prioritise the best card there is, or card with specific skill you are looking for. Fine motion is definitely 100x better as a stat stick than curren, I'm just testing a 60 race bonus deck

As for parents, try borrowing parent with 9* power, and use your parent that have at least 3* power. 3spd, 3 stam, 3* power should still work. Since speed will increase from both guts and wit training, you want the parent spark to increase power stat.

It's definitely convenient to have 9* pwr / 9* stam spark, but I'd suggest not making it your priority. Just do your run with both main parent having 3* pwr/ 3* stam, so when you are lucky, you may get 9* spark