I'm an entrepreneur and I'd like the begin investing. How much should I save up to start and where should I go for resources?

Thats exciting! Here are a few options:
Apps: There are so may apps that you can use to get started including Accorn and Betterment and they start you off slow.
Non-Profits: There are also several local non-profits that have investing for beginner classes that will actually match your funds, for example on here in Brooklyn requires you to have $750 and will match your $750.
Freelancer's Union: Lastly, if you are an entrepreneur, look into joining the Freelancer's Union, they have retirement plans specifically set up for independent workers.
Happy saving and congrats on thinking about this important aspect of your financial journey.