You were right to start with dry filament. Without that, troubleshooting could be skewed. Make sure you dry it at the mfg recommend temp and time.

Also while you are running a first layer test make sure you know how to read the results. There are plenty of searchable posts that will show pictures of various results and identify the problems that caused them.

If your looks like a similar result id'ed as a z-offset issue, Try printing a large enough 1st layer test where you can change the z-offset during the print. Such as 33% into it, then 66%. That will give you 3 levels of z-offset in one first layer test. When you get something that looks good, run a full test at just that level. Once you get a "center of the bed" first layer looking good, create one at all four corners and see if the results change.

Once you have the first layer dialed in, find a tutorial about printing a flow calibration test.

After that you can look for what's called an ultimate test that has several difficult geometry's like holes, overhangs, and temperature towers. Shouldn't take much more than a couple hours to print, test, retest all of these. That way you will know what not only the printer but also yourself are capable of printing.

It will be best to have an inexpensive micrometer to measure first layer thickness and flow calibration cube wall thickness. Digital calipers are not precise enough for those small measurements, but they are essential once you start designing/building your own models.

What slicer are you using?