Let's say I wanted to open a shoe store. But I'm not a major, well known retailer. However, I'd like to include brand name shoes in my store. A wide selection for whatever has demand in my society. I only want limited supplies because that's all I can manage with small business. Will I get any decent rates?
This is just an example. The idea I have in mind is very nice in principle. Problem is advertising/acquiring products I need at manageable rate until the idea grows. And I mean very large selection of various products.
I will talk in broad terms. Whenever you are running a business, you have to study the business model first and think carefully why this model is better/profitable than others.
If you have a lot of established players in the domain you are venturing you should never compete on the basis on which those established players are playing. They will ALWAYS beat you.
As for the decisions, I think it is always necessary to think big but act small. There is a nuance in it.
If you are a B2C model, then a lot of decisions could be tactical like seasonality of consumer pattern, how well discount offers take off and durability of your products etc. While making these decisions you need to think very short term and do with temporary measures. ( This would be the survival level )
But the growth of a business always will depend on how well you were able to perceive the potential growth opportunities . And to capture that, you will always have to think big else you will always miss the train.
As you said that your idea is very good/creative. Well one advice, a lot of times people think they had a 'aha' moment and they are destined to earn billions now which almost always never happens.
You success will depend solely on how well you executed your plan and that alone. You constantly perceive market changes and try to move from one winning position to another before others do so that when the day comes when "everyone" realises the market has changed, you are in the prime position.
You gave an example of a shoe but I am not sure what kind of business you will be operating for real so talked on very broad terms.
Good luck with your endeavor.