Help to choose vitamins, iHerb

 Good evening!
Two months ago i started to do sports. As i didn`t know that the right shoes are so important i did my fitness without sneakers. So i have painful knees now.
Can you suggest something to help knees to recovery?
I was searching a lot, and people advice to add some vitamins and supplements into my diet. I found a coupone on iHerb, so i decided to buy some on this site. Which vitamins can you suggest to buy?Do you like iHerb products?
For anyone interested in 10% off coupone , i leave it here, so you can use it.
Thanks!