I have one $500 card. I mostly use it for grocery shopping, restaurants, and any other various small purchases, since my debit card only gets 15 debit transactions per month before I start being charged for them (though I could use it as credit which won't add to that count, but it doesn't always work).
One, that I've had for almost 25 years, that I pay in full every month. It's pretty simple, in that it doesn't have any fancy features or "rewards" points. It does (I think) have a 1% cashback bonus that I get once a year or so - frankly, I don't pay much attention to that. I trust the bank (it's not a typical bank), and they've more than earned my business. I use this card for almost all purchases except for monthly bills.
I've got a debit card too, but I only use it to withdraw cash at ATM's once a month or so.
And yeah... I'd put the poll at 0, 1, 2, 3, 4,5, "more than 5". Wow.
Only 1 debit card. I'm wary of the banking system; policies change so radically that it can become difficult to minimize debt, while bankers often throw deals at you with several implications that they might not even be aware of. Plus, I hate the fact that most banks squeeze their clients because they are indebted to a pool of people even more significant than those who owe them. Analyze the process from the bottom up, and you see the drawbacks of capitalism in all their splendor.
Two--Mastercard and Visa. The Mastercard doesn't count because it's pretty much a dump for my financial aid and scholarships...just really a debit card. I don't use the Visa very much. And a regular debit card through my bank account.