If you are after tips, my offering of a few suggestions -
1. Use Stretch needles. Don't bother with ballpoint or jersey needles because a stretch needle is a more advanced version of ballpoint needle.
The ballpoint needle was modified to create a stretch needle that cradles the thread better and reduces cling and drag on the needle from stretchy fabrics.
They can be used with any stretch or knit fabric and are always recommended for sewing anything that contains elastane (elastics, lycra, spandex etc)
Mostly I use a size 12/80 Stretch needle rather than a 14/90 although I do use the latter on heavier, thicker stretch /knit fabrics)
2. On your machine have a play and practice on some different types of Jersey and stretch fabrics to see which stitches and settings work for you and the fabric. Also take a look at how to cut and attach round neck and Vneck bands to the neck of T shirts.
Have a play without any pressure
YouTube & Google are your friends on this adventure.
3. From a charity shop collect some Tshirts made from different fabrics. They don't need to be nice Tshirts. You're going to cut them up and use them for your practice sewing and stitch sampling.
Look for set in sleeves, raglan sleeves, round neck, V neck, placket+collar etc. See which styles DH may like and take a look at how they're made.
4. Find a pattern you like to start out with and check the fit. For the first couple of test T shirts, you can always make them as Pyjama tops.
Finally, adding length to your Tshirt pattern for a long torso is easy. Also, my DS2 has a long body and for casual wear likes a rugby shirt style where the back is usually a little longer than the front and there are side splits
Hope you enjoy yourself