What does sufficient capital look like to be successful in day trading?

For the first 3 years, if you have a $50-100k or more, you have a 99.9% chance of losing ALL or MOST of it!

Most brokers will give you 4x of “intraday buying power”. So for every $1 of real money in your account, you have $4 of buying power to buy securities.

After you learn that the markets have “elements of randomness”, you are confident in placing trades, you learn risk management, etc,

Having $50-100k is a good start. I know several that have much more.