Don't have more than three credit cards that you use. (Keep it at two).
False. My Credit Card setup:
Discover It (5% rotating categories)
Chase Freedom (5% rotating categories)
American Express Blue Cash Preferred (6% cash back at groceries stores)
US Bank Cash+ (Selectable categories I use this card for 5% cash back at Best Buy)
Chase Amazon Prime Visa (Amazon 5% cash back)
Target Mastercard (5% off instantly at Target)
Chase Freedom Unlimited (1.5% cash back I use this once a year it's an old account twice converted)
Citi Double Cash (2% cash back on everything my go to card when nothing gets a better rate)
That's 8 primary credit cards of which I use 6-7 pretty regularly. You can't maximize your cash back with 3 or less credit cards. 3 if you had the Amex I have, the Citi DC and maybe the Freedom or It would be acceptable but I'd still feel like I'm missing out.