First off, you hair is just gorgeous! And I can see why. You are doing so many things right already.
Fine hair tends to like protein no matter what its porosity. Protein shores up the inner structure of fine hair and helps it support itself. It varies from person to person, but a common routine for fine hair is a weekly protein treatment followed by a deep treatment (to balance the protein). Protein will also help keep your long hair healthy and strong. You may want to test a small section/curl of your hair the first time you do a protein treatment.
This link explains protein for hair.
The Fine Art of Protein and Moisture Balancing for Black Hair Care - Associated Content from Yahoo! - associatedcontent.com
Protein treatments: Ion effective care, joiko k-pac and sally beauty knock off (has mineral oil, which works for some hair and weighs down others), nexxus emergencee, IAgirl's gelatin PT.
PT recipe - as promised
Homemade FSG has a high success rate as a curl enhancer.
No-fail flax seed gel - I finally did it...TWICE!
Organix shampoos and shea moisture shampoo (some targets and walgreens) are popular.
For conditioner, I'd assume you want something moisturizing that won't weigh hair down. There are others here with those hair needs that will have more suggestions. Two I can think of are yes to cucumbers and tresseme naturals.
Crunch can be your friend. Crunchy gel holds your waves in place as your hair dries. Once it is 100% dry you can scrunch out the crunch (SOTC). Repeatedly squeeze your hair to break the gel cast until it is no longer crunch, but bouncy and soft.
At night, most people do what is called pineappling. It is a high loose pony tail on the top of your head with a scrunchie while sleeping. If your hair is too long for this, you could try braiding it loosely at night.
Here is a thread for people with long hair that might have some helpful info.
Very long haired curlies come share!
I believe one and only argon oil does have silicones.
Also, you sound like you may already be familiar with the curly girl (CG) method. But if not, this link helps explain it.
The College Curly: Laura Lee's All In One Guide to Going CG: Now Revised and Updated!
(a blog to help new wavies, go to the how do I get started page)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers