The minimum investment to buy Amazon would depend on the current price of Amazon stock and the costs associated with the stock or CFD broker your decide to trade with.
The price of an Amazon share should be around $114.41 a share.
Your other costs would be the minimum deposit required by your brokerage and any commission fees you have to pay for buying and selling your Amazon share.
You can buy Amazon Stock with a stock broker like Etoro or you can trade Amazon stock via CFD share trading with a broker like XTB both brokers should not require a minimum deposit to trade.
You can start trading straight away.