In my mind, private label and building your own brand/nich products is the way to scale on Amazon.

Having managed and dealt with my own and clients' Amazon businesses, I would have to say that the one key technique is to have a solid foundation.

A solid foundation has the following characteristics:
1) High-quality products that you would personally use. If you don't believe in your own products, then don't expect shoppers to buy them. Simple.

2) A great product title with main keywords, features, and benefits that make the sentence flow. You don't want to just throw in a bunch of keywords or use a one liner as your product title.

3) Using great product images will help shoppers make a purchasing decision. The only sense shoppers have is Sight so you need to bring other senses such as smell, touch, sound, and taste to life for an unforgettable experience.
Just like yourself, shoppers want to know what exactly they are getting, the more details your images portrait, the better it is for shoppers to decide.

4) Great copywriting for your product description makes a huge difference as you want to hit shoppers' pain point with a thought provoking question, then provide a generic solution and your solution as well. Be sure to include product benefits, scarcity, and also call-to-action in your description as well.

5) Running Amazon ads and other marketing strategies (i.e. giveaways, JVs, facebook ads, quiz etc). What better way to do so than offering great discounts to shoppers making the offer irresistible!

The above are some of the main techniques to build a successful Amazon FBA business. Keep in mind that if you care about your customers more than your competitors, you will always win!

Best of success selling on Amazon!

Eugene

1) Differentiate your product from the beginning.

Many new sellers start with RA (retail arbitrage), OA (online arbitrage) or Wholesale before to switch to PL (private label) just to find out 2 years later that they haven't actually built anything for themselves.

They didn't build a brand and don't have their own product.

Even with the PL, it's just another label on someone else's product. Very soon the market becomes overcrowded and they have to look for the next big opportunity.

You spend all that time and effort to find, source and ship the products and it's a waste.

2) Start big.

Imagine how much inventory you have to rotate if trying to scale your PL business from $1000 to $50K.
It will take a while.

Start big by crowdfunding your product modification.

Kickstarter or Indiegogo can get you to the next level in a matter of months while further testing your ideas.

3) Multichannel.

Start selling at Walmart, Sears, retail, eBay and so on instead of sourcing your next product.
It's much faster to scale your business when you already have something working, instead of trying to find your next product.
Once you've exhausted all your channel, then go add more related product to what you already sell.

I hope this helps and good luck with your startup.