I started with $10 sex toy style nipple suckers. The droplets are likely blisters that popped. Let them heal before continuing.
Initial sessions should be limited to 15 to 20 minutes, or pain/discomfort or a purple color presents.
Over time nipple / areaola tissue hypertrophy develops - not unlike a callous. I believe this is the main mechanism for nipple development / projection when hormonal therapy is not in use.
I prefer $23
SuppleNips now which I can wear 8 to 12 hours easily. They are better designed for this task and more comfortable. I'll often sleep with them on with no discomfort or irritation upon removal after about 3 months of training.
I use Astroglide Silicone lubricant. I can confirm this has not affected the SuppleNips with melting risk what can happen with silicone toys. I have a size 2 supplenips but am satisfied with the results of size 1.
I use silicone bands to maintain / train. I'll often place silicone bands (one or more) after a SuppleNips session.
Clear Silicone O-Rings (pack of 10) 10mm works for me, some may prefer 8 mm. At $5.95 for 10 these are cheaper and work better than a more expensive brand ($16.99) I tried called
nipplebands
Over the course of weeks and months, the size and projection of my nipples has increased. I have a size 2 supplenips but am satisfied with the results of size 1.
These changes you seek
should be considered permanent when you embark on this journey.