Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Consider all the languages that are likely to have
A. a major web presence, and
B. also don't consider any languages you aren't good at, or cannot easily hire someone inexpensively who is good at them. Urdu, for instance, is quite expensive to come by experts in. It's a thought.
C. also, a given language should have both a large 'web browsing presence' or internet activity percentage, and also a large interest in whatever you are selling.
Consider security also. Your website 'has money' (and goods) so it should be more secure rather than less secure. Your backend admin page must have a good password ***** access to it, for sure, no matter how inconvenient you may find entering a good password. And, you should not share the password ***** much. The fewer who know it, the fewer can betray it - expensively for you, at the very worst.
Not that I mean to be alarmist! but this is a consideration that, if followed, will see to it that it seems 'alarmist' forever - hopefully. And that's a good result.
Make sure that, for payment, you use a better name of merchant or credit-transfer facility. Paypal, not NoNameMoneyTransfers.com, for instance.
Do you need basic considerations (the above cover most of it, plus what you mentioned)? or advanced considerations of what a good e-commerce website needs?