For everyone struggling with clothes sizing and having a hacker mindset, I can't recommend enough buying a sewing machine (~100EUR on a used market, ~150 new gets you a reasonable starter one you won't outgrow any time soon) and giving clothes alterations a try. Finding a tailor that understands you / you agree with is an option too, if time is a hard limit (though I'm not sure it's altogrther that much quicker). In…
Is overlock a necessity?
For some basic jerseys (think T-shirts) a basic zigzag is fine to begin with. That 100EUR sewing machine will have some fancier stretch stitch options that are slow, but "good enough" to look like an overlock (but can't do the cut of course).
If you have the space / money, overlock is definitely what I'd get as a second / third machine. It's much quicker / cleaner if you're working on jerseys or shirts.
But I still keep wearing the T-shirts I did when I was starting. On my list the first thing to do is to understand how to alter something to fit you. It can be done by hand (needle and thread), but to be reasonably efficient, the BOM would be "sewing machine, box of pins, scissors, piece of chalk / ruler and something to press / iron".