I recommend adding apps that increase your conversions. Not sure what you mean by design apps but your theme is the design, apps just add some extra functionality to your store, like a countdown timer or the ability to import products to dropship (Oberlo).
For conversion increasing apps, I wrote this guide a while back with 8 conversion increasing apps. The main ones are:
This app lets you display 3 key countdowns: deals, stock, and the number of people watching the product for extra social proof.
Displays a pop-up with recent purchases people made on your store. Can be tweaked and customized. Very good way to show visitors that other people are buying from your store (social proof).
This just allows you to add second products as up/cross sells at a discount when you buy them together. Fantastic way to turn a $20 customer into a $50 customer and ramp up that average order amount.
- Koen from 21Brands.com
The above recommendations are all excellent. We particularly see Yotpo used on many stores for reviews.
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