Help with a plan to restore dry, coarse, brittle hair :(

I have very long (waist length) hair that I believe is majority 2A. The individual strands are incredibly thick, however the underside of my hair/the nape of my neck is is a completely different texture than the rest (also not sure what causes this???) but it is VERY coarse, wiry, and dry - it also naturally curls up a lot better when or if I use product.

Growing up I used drug store products, a lot of herbal essence and pantene. I splurged last year and got huge bottles of Moroccan Oil shampoo/conditioner set when it was on sale. It worked for awhile then not as much recently (maybe it just got old?). After those bottles ran out a few weeks ago I got Maui Moisture in a pinch and it has just left my hair SO DRY and frizzy.

my questions:

1. Shampoo/Conditioner recs for dry, frizzy, thick, coarse, wiry hair - something REALLY deeply moisturizing (my hair I swear never gets oily, if anything it always needs more oil)

2. Is it not a shampoo/conditioner thing and more of an "accessory product" thing? Like should I worry less about Shampoo conditioner and start using leave in conditioners, hair masks, oils, creams more etc?

3. If I do use those extra products, how frequently should I be oiling, masking, washing, etc?

I JUST WANT PRETTY SILKY FRIZZ FREE HAIR! :(