How can I define the coordinate system of a spline aligned with 1st spline vector?

I need the coordinate system well defined (better than just the origin positioned in the 1st vertex).
I need at least 1 axis of the coordinate system aligned with the 1st axis of the spline.
How could this be done?
Here is an illustration of my problem, in the pic just the origins match, but no axes:

I need this for properly positioning objects for path animations along this spline.

What I need to achieve is aligning an object z-axis with the origin and direction of the 1st spline vector. Maybe that could be done in a different way?

Many thanks for any help!

Use normal transform orientation for moving and create a custom one for other objects.

My question would be: how do I create a custom transform orientation (for the spline / one axis parallel to the 1st spline axis)?

The one method I found: move the object to 0,0,0 and rotate so its axes are parallel to world xyz. Then press “apply”.

Custom transform orientation (TO) can be created with ctrl+alt+space. List of them is in 3d view properties.

If the object local axis need to align with that, could add a hook that keeps all control points in place, and then object -> transform -> align to TO, without doing the same for the helper empty. Then apply the hook.