For filling seams, you can't go far wrong with putty. Squadron's green putty is what I use the most. Apply with a cocktail stick, hobby knife blade or some other tool you find suitable, let dry, and sand smooth. Letting the putty dry completely before sanding is essential, since some putties contain solvents which melt the plastic a little, same way as styrene cement, making the putty stick well.
Your build looks pretty good so far. Some seams could use some filling and sanding, though. When you go out to buy some modeling supplies next time, invest in a file or two, they will come very handy. (like the slight mismatch of fuselage halves in the frontal air intake for example).
I really like the way you got the decals attached, no silvering at all. I presume they're from the academy kit? Impressive, I have never succeeded in gettin academy's decals to settle down without silvering. No matter the gloss surface underneath, or microsol, they silver.
One more thing. Please, refrain from posting very large pictures.
Depending on one's connection, they take largish to humongous amounts of time to load, and force people to scroll the page not only up and down but sideways as well, both to read the text and see the photos. IMO, 800x640 resolution is quite ideal. It doesn't spoil the details, don't take ages to load, and fit almost any monitor nicely. Nothing wrong with you photography, the pics are nice and sharp, they're just huge. A little cropping and resizing would make them much more pleasant to view.