Depends on your budget, really. Is it worth you to get basically 'disposable' shirts?
I have had some organic cotton Tshirts last me 13+ years now and they still look great/color, etc. They cost at the time 15$ or: a little over 1$ per year.
I just loaded up on some shirts from Uniqlo because of a comment a friend made on their clothing that they last a long time (10+ yrs)-and she has way better judgement in clothing than I do...for sure. So there basic T is 10€, but I got a deal on the first order through their website & got 10 for 6.50€each.
That being said, I would load up on these and have them in stock at home and get a much use out of them as I could (and when they wear down they're hobby/work/outdoor etc.)...
Edit: wash in cold water, do not use fabric softeners, and only 1-2 T of detergent, line dry if you can