A quick dash through the charity shops on Saturday morning, for men's shirts, and then a few hours of sewing, and I have 3 new 100% cotton tops for R30 to R40 each.
I used the 2 Hour Top pattern from Sew Different. It's a free pattern! It's only available in 1 size, but easy to scale up or down. I took off 3cm on the side seams, and 1/2cm on the raglan seams. (Looking at these photos, I think next time I'll only take 2 1/2cm off the side seams.)
On this shirt I cut out the neckline a bit further than the pattern, and the sleeve and hip lengths are unchanged from the pattern.
Shirts without pockets are obviously easiest to work with, but if the fabric under the pocket isn't noticeably less faded than the rest of the shirt, you can take the pocket off and put it somewhere more useful. You'd probably need to take the pocket off to fit the front pattern pieces into the available fabric, so do check the condition of the shirt carefully before buying.
These 2 were short-sleeved shirts to start with, so my sleeve length was determined by how much fabric was available. I kept all the original hems, which made things even quicker.
On both these shirts I used the neckline as drawn on the pattern.
I didn't have binding in the right colour for any of these, but I did facing/binding thing that worked quite well. It takes a bit of ironing and fiddling, but not bad for a first attempt, don't you think?
I folded the sewn-up shirt in half, traced the neckline, cut a facing, sewed it on, then cut it down to binding width and sewed it on like binding.
A note about sewing with charity shop shirts: wash them before you start sewing (I'm looking at you, Salvation Army Shop). Though perhaps generally it might be nice for people to wash clothes before donating them to charity shops.