Let me just say that I only read the outter planets in a natal chart if they make a strong aspect to the sun, moon or ascendent. For many people the outter planets are strictly generational and the energy of the planet isn't personalized. For example, in your case, with neptune near your ascendent you will interface with the world using neptune's energies and pursuing those interests. And I tend to disregard any outter planet orb more than 5 degrees.
You first need a good, clear idea of what the ascendent represents. It is our method of interfacing with the world. So, it's how we see the world and how the world see's us. It's the color of glasses we put on and our physical appearance. If you accept the concept of karma, it is the personality we are using in this incarnation, our costume. It is the most immediately "me" point in your entire chart, contrary to the notion that we "are" our sun. We "are" our ascendent and we are learning to become our sun. But since the ascendent is a point in our chart, it is not an energy, in and of itself. It is more like a tool used by the other energies which are represented by the planets.
Next you need a strong grip on the concept and symbolism of neptune. What does neptune DO? Well, one thing he does is create illusions, including the illusion of glamour. He also creates faith and our ability to merge with the universe. But those are just a couple of his meanings so we can use them as an example in your case. Thus, you may use your tool, your body or outlook, via the energies of neptune. You might feel impelled to work for the good of society or read tarot cards (hehehehe) or dress in a very glamourous fashion. All of these are possible interpretations. You might also be drawn to glamorous people.... you could be a groupie. Those are sort of pure neptune interpretations without taking into consideration the sign on your ascendent. The next step is to blend the energy ideas of neptune with the "how and why" that is symbolized by your rising sign. So take all of the possible meanings of neptune and try to decide what is the most likely interpretation of him acting in Sagittarius, which is ruled by jupiter and is therefore expansive, philosophical, etc. Think big scale. Where could neptune act out on a large scale? Well, from a religious pulpit, is one possibility.
Regarding the aspect between Pluto and Neptune, while it's interesting, I wouldn't try to blend that in unless Pluto is aspecting your ascendent by less than 3 degrees. The Pluto/Neptune aspect is a very long one and is, again, more generational than personal in nature. Let's just say it's an combination that will make Neptune more persistent and a bit less foggy for everyone born with that aspect.
