Open Question: Questions about credit cards and rebuilding credit?

My husband and I declared bankruptcy about a year ago. We are trying our hardest to rebuild our credit and get back to a good place. He has two credit cards already, but they are in his name only. I want to get credit cards in my name. How many credit cards should I have? 2? 3? Should I apply for 2 or 3 credit cards all at once? Or should I space out my applications (or does it matter)? Is it ok to apply for 2 different credit cards from the same company (eg. 2 cards from Capital One?) Should my husband and I get a joint credit card? Thanks for your answers!! (By the way, so far he has done a good job with his credit cards and paid off the balances every month. He hasn't gotten a single interest charge. The only thing I'm worried about is the first credit card he got - it only had a limit of $700 and we got pretty close to the limit one month, but we paid off the entire balance. I read somewhere that you should only use 30% of the balance available because creditors can see your "high balance" when they run your report. Is that true - is the amount you use more important than when you pay?)