This is largely a matter of personal preference. Generally, males will be larger than females of the same breed, but often the differences between genders are fairly subtle. Examine the FAQs for dogs and cats to find the answers to these questions. You'll want to have a litter box for each cat in your household and at least one box on every floor, and find time to scoop it daily. Cats are fastidious creatures and prefer to have a clean toilet area.
Training takes time but is well worth the investment.
Additionally, behavior problems are less likely to occur in an animal that has received basic training.