If you're starting with a relatively small budget, Magento offers the huge advantage that you can launch quickly with a minimum feature set. You can always improve and change your website at a later time, because it is open source software. Launching quickly means getting indexed by search engines quicker, and being able to test how to get customers quicker. The work on your store is never done. Trying to emulate the giants, such as Amazon, when you launch is impossible, so try not doing everything under the sun before you have even had one order. This goes for all aspects of your shop: marketing, sales, purchasing, customer support, and so on. You will only find out what's really important after you go live.
That said, your store should at least look reliable and work properly. Do not give your customers the impression you threw it online in a weekend. There are a number of ways to achieve this: good content, a nice logo, a well-picked theme, and more...
