Register your domain name with a reliable service. Prices differ based on the domain extension (e.g. .com, .sg or .org) and your chosen registrar.
As a benchmark, it costs $29.96 a year for non .sg domains while .sg is $58.85 annually. Remember to opt in for auto yearly renewal so you don’t lose your domain name. To make things easier host your site with your domain registrar.
You will also require a web hosting service to host your website. There are platforms that allow you to easily build an e-commerce store, or if you're looking at just a web hosting service, there are many service providers available. Do a little bit of research to find a reliable service provider and look out for terms like "Storage capacity", "bandwidth limit" and "server uptime".
For your day-to-day operations, ensure you have a reliable connection to update your website or manage incoming orders and enquiries. Consider SingNet business fibre broadband, with benefits including high-speed symmetrical internet access (between 100Mbps and 1Gbps), access to 24x7 technical support and capacity for concurrent wired and wireless connections to reduce traffic congestion.