If you can play the game to your rules, not theirs, having a single credit card can be ok:
* Pay the entire balance every month, ideally by direct debit (they don't like doing this)
* Ignore offers to increase credit limit
* Actively reverse automatic credit increases. My card company tried ridiculously hard to talk me out of reducing my credit limit.
This type of credit card customer is by far the minority (10% iirc), and least welcome to the card companies. Their ideal customer has multiple cards and pays minimum balance every month.
Student loans also count towards credit worthiness.
For a home loan, having little or no credit, isn't necessarily a deal breaker, but does limit lender choice. At least in the UK.
I dislike the game partially because the more indirection between spending and the actual money, the easier it is to overspend or lose track. This is the whole point, of course! So I just stick to the debit card for net, and actual cash from ATM when out shopping.