How much time to get traffic in a new e-commerce website?

How long is a piece of string? How competitive is your niche? First off, don't be drawn into the lure of big pay cheques - it's going to be difficult. You can typically begin to expect seeing results in the first 3-6 months,(for generic terms), but providing you start link building early enough and build enough high quality authoritative links to your site from a diverse range of sources, search can begin contributing long tail traffic relatively quickly. If you're looking at building an e-commerce site then I would watch out for issues such as pagination, accessibility and above all else, wide-scale duplication.