Done glider flying in the 1980's, I hated it!
There is little correlation between the ability to land a double engine failure in a 777 and the ability to fly a purpose built glider down to the field! My opinion of course.
If you want good handling technique including the necessity to use the rudder, fly helicopters.
I am not saying gliding is for everyone. Fly choppers all you want.
And with regards to landing an airliner with full loss of power. Well, I will say this: if you learn the correct things from gliding, you WILL be able to apply them to anything.
This is IMO. I think plenty will agree, and perhaps plenty will disagree. Although IIRC there have been a number of incidents in the past where gliding experience has helped (and arguably saved the lives of many). Gimli Glider was a good example of just that. Whether or not the Captain's gliding hours have helped is open to debate, but a large number of people think it has.
I am not saying that gliding experience automatically gives you the ability to save the day. No it does not. It gives you a slight edge because you will learn how to manage energy better (if you do), and by advantage it may be anything from 0.5% to 20%.
Why do glider pilots constantly feel the need to go on about how gliding makes you a better pilot. Arguably almost all flying makes you a better pilot provided you're not boring holes in the sky mindlessly picking up bad habits.
Gliding is great, I've done a bit, but it's not for everyone and there are plenty of ways to improve your handling skills with an engine in front of you too. I also can't see how gliding helps much towards a commercial career, which is essentially what this bit of the forum is about.
Get relevant hours in your book that count towards your licence, have fun doing it and keep your mind on continually bettering yourself.
For the record I have 4 hours gliding time. And 90 hours SEP time.
Flying props is much more relevant to becoming a commercial pilot - I agree. But there are very very VERY few piston aircraft that will teach you about flying as much as gliders will. And by "flying" I mean actual stick and rudder flying.
And you can also do aerobatics and spins in a glider for a fraction of the cost of a Decathlon, never mind a Pitts or an Extra. And even if you think that gliding on its own doesn't make you a better pilot, aerobatics do. And there is definitely no argument there. Just depends what you decide to take away from the experience.
Also, I hadn't suggested that the OP does gliding as a means of achieving a CPL. As you can see that was not his question. I have just suggested this, as opposed to being a "pilot assistant" - a role that doesn't actually exist. So my point is - if you want to learn about what flying is - go fly some gliders.
Of course you will need some good prop experience! I am by no means saying that gliding is any kind of replacement for props. But IMO it will greatly add to your ability and it will make you a better pilot.