First of all -- remember that learning to use a DE razor is a skill to be developed, not something you simply pick up and run with it perfectly within a few shaves.
Below, based on my experience, are the most important points to remember along with a few thoughts and suggestions for you.
1. Blade angle
2. Razor pressure
While I have been doing this for many years, I consider myself far from "sage" material, and note that I have much yet to learn.
However, I will say that the neck can often be the most difficult area to get right. When I first started off with a DE razor, I had issues with bumps and irritation on the neck for several weeks before I realized that my angle was still off and my pressure was too heavy - even after thinking I was paying close attention to technique.
Even now, if I am not careful and watchful, hubris will sometimes set in and I will come away with some irritation on some place on my neck as a reminder that I was not paying attention. It doesn't happen often, but can easily come into play.
I suggest that you may give shaving a miss for a few days and let your neck recuperate. The edge of a DE blade is really, really sharp, and can be quite harsh on the skin if anything goes awry. Then I the next time you shave after 2 or 3 days off - only do a light pass with the grain on your neck. This is normally from the chinline down towards the chest, although you will need to check your whisker growth pattern to be sure. Necks are a very nefarious thing when it comes to shaving with a DE razor as you have found out yourself so patience and care are the watchwords.
New DE users tend to want perfection their first time out. Worry less about the perfect shave and bbs results, and more about getting the technique right first. I learned for myself early on that "just presentable" was better for me than "redneck spots" because I was trying too hard. FWIW - I would say it was a good six months before I felt entirely comfortable with my results and changing up my tools at whim.
And one other thing -- try to keep your set up exactly the same. The more variables you introduce to your routine early on, the more difficult it will be to develop proper technique. For example, I used only US Persona blades, a '59 Fatboy, Vullfix 1069 OEM brush and C&E Sweet Almond Oil cream for my breaking in period. Others will likely share similar comments so take it all in, don't try to be perfect out of the gate, and you too will be rewarded --- however, Never, Never, Never .... give up.