First, some simple instructions: here are the steps I take in setting up a dynamic cloth to fit a figure. When starting with dynamic cloth, you want to start easy.

Make sure that the cloth does not intersect with the figure anywhere. This is not a hard-and-fast rule, but if your sim crashes or the cloth starts looking weird, it's the first place to look: for poke-throughs.

Loading your figure: you will want to pose her in either the default zeroed pose using the joint editor, or using whatever the cloth maker provided for zero-pose in frame 1. That's the slider thingie at the bottom of your workarea (typically). Check that your figure isn't translated anywhere from 0, both for body and for hip. Also, to start with, all morphs need to be set to zero, including custom morphs. You can do that easily with:
Menu: Edit -> restore -> Figure
(thanks for that, Laurie ). Those morphs do come back, including expressions, in the final frame.
Posing: let's say we use the default 30 frames. Go to frame 30 and make it a key frame (click on the little + next to the church-key-looking thingie). Pose your figure, including all your morphs and expressions.

Move your slider back to frame 1, watrching all your morphs and pose fade away. In frame 1, load the cloth to be clothified on your zeroed figure. Dynamic cloth is generally stored in the Props folder, with rare exceptions. Have a spin-look around your figure at the cloth-prop: there should be no poke-through anywhere. Make sure it is parented to the figure.

In the Cloth room, set up a new sim. Click on New Simulation...

• 1. Cloth Simulations: click on New Simulation. For Simulation Name I tend to call it by what I'm clothifying: short version. The only other change I make in this dialogue is to tick the Cloth self-collision tickbox... and click Ok.
• 2. Cloth Objects: click on Clothify... oftentimes your item will be selected. If not, you'll have to search for it under Props, for the most part. Click Clothify. Click on the Colide Against... button: click on the Add/Remove button and select your figure, the one wearing the outfit. The next values are suggestions: they work for me as a starting point. I set collision Offset to 0.25 and Collision Depth to 0.2.  Please keep in mind you may want to adjust those values up or down, usually up, of the pose is a bit demanding on the cloth. Tick "Ignore head, hand and feet collisions if the cloth has no chance of intersecting with those body bits, and click okay.
• 4. Dynamics Controls: Click Calculate Simulation.

If you have more than one item, you want to do this for each item.

If the gurus see something I've missed, please point it out to me. These steps are what i take, but I may be labouring under a misconception about the workings, so please do let me know.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks