Low conversion is to be expected when you are just throwing out affiliate links to cold traffic, especially Twitter, since they are well known for not converting too well. A way to increase the conversion rate would be to warm up the audience before selling them something.
You can try to create a landing page which will presale the item before you send them to Amazon. Optimizing the landing page will may be the biggest challenge, you could search for similar landers and try to copy their style, or experiment by your own and see what converts the best.
Or if you wish to put even more work and time on it, you can go one level beyond and create a setup like this:
- create a Landing Page with an e-mail opt in, maybe offer some valuable resource related closely to the niche of the product (free ebook or something similar) in exchange for their email, and instead of promoting the Amazon product, you promote a "free whatever".
- Build your email list. You will collect emails of people that you KNOW that have some interest in that particular niche, since they already downloaded your free resource.
- Create an email sequence in which you will be sending them emails containing some valuable information about the niche
- After a few info emails you can you can start throwing in a link to the product, explaining in detail how that particular product will be of use to them.
- You can continue to alternate between a value email and a sell email after that. Since you have the list, you can find different such products that you can promote to them in the future.
This way, when you try to sell something to them, they will be much more warmed up, and will have built a trust with you, so they will be much more likely to buy whatever you are trying to sell to them.
This requires some bigger investment and work beforehand, but is definitely achievable if you put your mind to it. And is not specific to Twitter only, you can use any other social network.
Though, this may be more suitable for products from Clickbank, or some more expensiveAmazon products or offers, because of the relatively low Amazon commissions. Also, it is more of a long term project, since building a good list takes time, and it will take a while for the whole setup to start working, but having a good list it is definitely much more profitable in the long run.
But if you are looking for some quick easy cash you can continue doing what you do now and scale it with more accounts. Maybe experiment a bit with your tweets, try some clickbait titles, add some eyecatching images or videos etc.