Suppose I raise $10 million from venture capitalists for my rocket startup, what are the initial steps I must take (as a person with no experience of making rockets before) to ensure my companies growth in a successful gradual manner?
Become an investor in SpaceX. \$10M is not enough to start your own rocket company (it takes at least \$1000M), but it would be enough to be taken seriously as an investor in another company that has a record of success, yet still needs cash.
Become a subcontractor. Build something that a larger company doesn't do themselves, but might be willing to buy from you. For example, one could start a company that makes space food.
Citing comments of @Tristan and @Polygnome:
$10M will pay ten people pay and benefits for maybe 5-7 years. That doesn't leave any money over to get any hardware.
Well, Elon musk invested about $100 million from 2001-2006 of his private money into SpaceX. Falcon 1 would not achieve orbit until 2008, and that has only about half a ton worth of payload. That should give you an idea.
I would add to them, that although $10 million is not enough for orbital rocketry, you can still join an already ongoing private rocketry project as a business partner or as an investor.