At first with limited capital, you have to invest very prudently. You need equipment that is broad range or universal. And you better have wholesale or mooch connections.
Then let the market dictate what you start stocking. My biggest demand is water lilies, so I find the least expenive source in the US and propagate my own. I sell to wholesalers now.
Another consideration is commercial applications. You may have to spend more to get professional or commercial grade equipment, but in the long run, you come out way ahead. Customers have a perception factor, if you break out DIY equipment on the jobsite, it leaves a bad first impression. If you pull out that professional equipment, you look like a pro, and like it or not image is everything, at first. Then it's up to you to do the job right.
Exotic species, slow movers are dead weight, money burners. I let my local market dictate what I stock, and what I load up on. I am not in the business of pitching and selling, I am a supplier and consultant.
