Build an Online Store

I am looking to build a combination blog and e-commerce website for a starting home-based small business where I sell hand crafted clothing and curated accessories. I would like 3 things: - Give the customer an ability pick an item from a selection of a few fabric swatches. So, the variants would need to be image based. - As the company is travel oriented, I would like to build a map of the world, where i can stick a virtual pin where I have traveled relative to the origin of the fabric or accessories - My issue is that certain items use more fabric, and depending on the person's size, the amount of fabric required to make the item will be different. Example: person size 10 will order a skirt. She selected fabric A, requiring let's say 2 yards of fabric. Person size 20 orders the same skirt and same fabric, but it requires more yardage. How can I adjust my inventory on the website to account for stuff like that? So the system intelligently knows that depending on X size and Y product, subtract Z yards from inventory so what is shown as available to the customer is always accurate, whether it is available or sold out. I would like to be able to maintain this going forward. i'm fairly technical, and used to code, but i'd rather outsource to an expert. I've been told that the combination of these three 'wants' are impossible and ridiculous to maintain. Help!