Step #1. Select lens.
Step #2. Determine your personal abilities with regard to photography. Do you need customer service and hand holding to use/own the lens selected in Step #1??? Or are you a self-starter and able to get thru life without someone holding your hand?
Step #3. Based on answer to Step #2. If answer is "Yes, I don't need a dealer to hold my hand." Then use internet search engines to search for lowest cost pricing internationally and have lens shipped to you.
If answer is, "No I need dealer support." Then use internet search engines to find local camera dealers within your geographic area that are listed dealer by brands.
Since you've use the internet to find this place and ask the question, I'm assuming that you have the technical skills to proceed to Step #3...
Good luck with your quest to find a source for your purchases.