You pretty much have the right idea i think.
HP is going to be one of the key stats you can acquire.
Mana and int is important too to a certain degree but with necros HP is your lifeline in a lot of ways
Other then being able to take a bigger beating, you have more mana to funnel with higher HP via lich spells.
Higher HP = Less waste from life taps exceeding a lower max hp.
Specific Items to look for in the future besides the ones you listed..
Theres always the epic of course but something that you should really keep an eye out for is..
https://wiki.project1999.com/Encyclopedia_Necrotheurgia
I think that book stands out the most to me. Look into it.