"I replanted it with good potting mix"

What kind of potting mix?

This kind

Ahhhh OK. I also got a warnecki plant that seems to be thriving in it. So in two weeks, the plant is just too moist? Are limp leaves the sign of too much water? Note that I'm new at this and just went by what the guy at OSH recommended.

The plant may be dying of thirst in a sea of plenty. What this means-the soil is so saturated with water that all the number of air pockets are either gone or significantly reduced. Without oxygen, the roots start to suffocate and can't function properly to hydrate the plant.

In a fast draining soil, there are plenty of air pockets so the roots can breath and function normally. Your plant should look better once it's potted in a fast draining soil.

Now, I could be wrong and the plant may be adjusting to its new soil, but from what I've read the readjustment time for repotted plants is roughly around one week. If yours is still wilting like that after two weeks I think it's something to be a little worried about.

Does the pot have a drainage hole?

OK got it. Off to get succulent mix and perlite. I have some little succulents to repot as it so happens. Should I blend perlite in for those as well?

Yes. 50/50.

Potting soils like the one you purchased can be very useful in hanging baskets, or outdoor raised planters and pots --- particularly if one lives in a very arid region. But indoors it is typically a very poor choice for many/most plants.

As Goldstar mentioned, wilting can be due to lack of water or overwatering. In the latter case, the roots suffocate and die which results in the plant having no means by which to take up water which, in turn, leads to wilting.

If buying perlite, try to get one without added fertilizer.

Also, polka dot plants generally do not make very good houseplants. They are usually very resentful of the dry warm air found in many northern homes -- particularly prevalent over the winter. They also may get very etiolated without sufficient light.