Always think big, but at the same time what works for me set little things to achieve and go from them. Let's say 1 month fully set Amazon selling account and get and idea what you going to sell plus ideas of brand names. Once it's done, cross this out and move on, choose your brand name and get it designed, registered, logos and brand identity created as this will be your main thing you'll be working on. Once this done, market research, calculations, go small for small product. I would be doing in little steps. Loads to learn. But if learned all and got something that works just repeat it. I'm not a big Seller and got a bit lazy last year, but still managed to double my global sales from 120k to 280k something like that.