Macro Extension tube with AF : how to use best ?

I just bought this Macro Extension tube with AF : http://www.benl.ebay.b​e …geName=STRK%3AM​EBIDX%3AIT

With which of my lenses below would it work best ?
I just tried with my 24-70 and 17-40 but had to put my lens almost against the subject.
Would I start with all the rings so that the lens will be most far away from my camera ?

First off, using it with a zoom lens is a recipe for insanity - the focus point will change as you zoom to adjust the framing.

Second, the longer the extension tube length you're using the closer you'll need to get to the subject to achieve focus (and the greater the magnification will be).

Start with the shortest (13 mm) tube on your 135 mm lens and see how much closer you'll get. Remember, by adding any tube to any lens you'll lose infinity focus. Then move to progressively more extension and see the differences. Just using the two longer tubes stacked with your 50 mm lens will get you to about life-size, and a 100 mm (or less) working distance, depending on the internal optics of the lens.

I get 1:1 with 25mm ET and 18-55 STM at ~35mm, on a 70D. ETs work better (more magnification) on shorter lenses. If you can't get focus at all (think 16mm on 16-35 w/31mm ET) your focus point may actually be inside the lens.

In past I had a Sigma 150 2.8 Macro but sold it, as I realised and read I need a 5:1 magnification for the pics you sometimes see of gigantic insects.
This is probably not possible with this extension tube and one of my lenses ?
I'm not going to buy a macro again as it was just for testing...

No, probably not. You can get better than 1:1 with the 50 and all three tubes, but unless you've stunned or killed the insect, you'll have a hard time getting close without scaring it off.