I do not like Anmgar or Trollshaws.
Angmar is group heavy content. A lot of group required landscape There is a considerable content that you are not going to be able to do because there is no one up there. The ones that are up are probably like me - picking the low hanging solo fruit as we are leveling before going somewhere else. Come back later on to do group instances with very high level characters
Trollshaws has very little content in comparison many other regions. A lot of the content is again group content in areas with a lot of mobs that require a group to bring down. Tal Bruinen was added later is very solo friendly.
North Downs is best of these three for leveling. Most people these days bypass North Downs for Evendim which is a better choice.
If I had to buy quest packs. I would do Evendim, Forochel and Eregion. Those did not work together because there is a gap for you. I would consider other choices. One good possibility is buy the Path of the Fellowship pack which would give you Eregion, Trollshaws and I forget what else. Do not even mess with Angmar. Buy Forochel and Evendim.
Unless stated otherwise, all content in this post is My Personal Opinion.