I'll throw out a couple examples I use. I have an extraordinary amount of fun with this new ability.

First to answer some of your questions. Immanence can be used to both open and close an SC. It can also be used to solo any SC if used twice, once before each spell. Immanence is NOT required to MB off of your SC, and in fact if you use Immanence before a spell, you will not be able to MB with it, as per the ability description.

All of the following scenarios work:

1. Immanence + your spell
2. Your own WS

1. Immanence + your spell
2. Another player's WS

1. Your own WS
2. Immanence + your spell

1. Another player's WS
2. Immanence + your spell

1. Immanence + your spell
2. Immanence + your spell

1. Immanence from another SCH + their spell
2. Immanence from you + your spell

1. Immanence from you + your spell
2. Immanence from another SCH + their spell

To get it to work right, first you need the right timing. This just requires practice but the window is pretty large. If I'm soloing an SC using two spells, first I use Immanence then cast the first spell. When my on-screen character's arms come down from the cast, I hit Immanence again, then immediately start casting the next spell. If I want to create a level 3 with Retribution or Black Halo, I wait until right at the end of the first SC animation to hit the WS macro. If I'm doing spell + my own WS, I wait about 3 seconds after the spell animation to hit the WS macro. I also have some macros just for making my own SC. Here's a basic example:

/ja "Immanence" <me> <wait 1>
/ma "Fire" <t> <wait 5>
/ja "Immanence" <me> <wait 1>
/ma "Thunder IV" <t>

You may have to play with the wait numbers, and vary them based on your first spell, but for me 5 seconds works well for tier 1, 8 seconds if I open with tier 3.

Second, you have to use the right elements. Disak gave a great example of the combinations. I used the skillchain chart on wiki. I never played a melee job before this so I had to stare at the chart a bit to understand it too. The chart does not contain SCH spells, but basically you just look at the element picture behind the set of WS's and pick a combination of spells and WS of those elements. For example, the label on the chart for Distortion shows it being created from Light, then Earth, so use Luminohelix, Stone. The chart shows Fragmentation coming from the ice picture then water picture, so use Blizzard + Water to make fragmentation. Here are some examples:

Immanence + Luminohelix
Immanence + Stone III
>>>>> Distortion
You can then MB any Water or Blizzard spell afterward. If you want to MB with a tier V spell, you will need to follow the SC with Alacrity before casting. I believe the same is also required of tier IV spells. I generally MB this with Cryohelix, for which I use Ebullience. Alacrity is not required to MB Helices on your own SC.

Immanence + Fire
Immanence + Thunder IV
>>>> Fusion
MB with Fire of any level or Luminohelix

Immanence + Luminohelix
Immanence + Stone III
>>>> Distortion
Retribution (Gravitation = Dark + Earth)
>>>> Darkness

Immanence + Fire
Immanence + Thunder IV
>>>> Fusion
Black Halo (Fragmentation = Thunder + Wind)
>>>> Light

Immanence + Fire IV
True Strike
>>>> Fusion

Now for some mechanical stuff. First, if you're in a large party or alliance, the timing can be rough because other players are constantly spamming their WS's, which will interrupt your SC. If you want to practice this, I suggest soloing for a while on a set of EP mobs to get the timing and combinations down. For me, the potential to solo Light and Darkness made me excited about finally getting Black Halo and Retribution, so I practiced using Immanence just to break the latent effect on the trial weapons. After that I've never had any trouble with timing.

Another annoyance may be the absence of the spell or initial SC animation due to gear swaps. If I or another player near me swaps gear, the game will not show the animation for the spell or SC and it throws my timing off. I got used to putting only equip swaps that don't require blinking into my Immanence spell and WS macros. For other gear I'll swap it with separate macro before casting. This gear blinking will also occasionally prevent the chat log notification of the SC as well as the animation, so it may not look like it worked at all when it actually did. When you're practicing, this is another reason I suggest doing it solo, and to also avoid equip swaps in your macros at first.

Hope that helps! Again go practice by soloing. Grab some EP+ stuff so you don't kill them with your first SC I used Kuftal Tunnel crabs to break latents and practice this. You asked specifically about making an SC with a WS, so to keep it simple, just start with Immanence + fire, wait three seconds after fire casts, then hit a True Strike macro. You'll get Fusion Don't forget Adloquium so you can use True Strike faster!