Okay, here's my take on score improvements.
To start with, it's generally wise to indicate whether the score is CONCERT or TRANSPOSED. You can put this in the top left corner of the score. (Yours appears to be transposed.)
I notice in measure 1 you have a poco cresc that appears to crescendo to "pp" from "pp." If the dynamic is a sudden departure from what's expected, you should probably notate "pp sub" or "subito pp" or something like that. This lets the players know that the dynamic is different from what they were previously playing.
I'd be careful using simile in the era of copy and paste. Handwritten scores and manual typesetting is one thing, but it's less ambiguous to simply write out what you mean rather than use the simile shortcut—and it's very fast and easy to do nowadays.
It's nice if the bar numbers are notated below every bar. If I were a conductor, I don't want to have to count 4 bars from measure 15. It'd be much easier if I could just look immediately below and find the bar number.
In a similar vein, you don't have to hide unused staves. It's far easier to follow along with a score if the instruments appear in the same line of sight on each page, even if some instruments don't play for several more pages.
You might split the horns out into 2 staves the whole time.
Measure 36 begins an arco passage immediately preceded by a pizz passage in the celli. I question how feasible that is.
No need to write solo (as in m. 42). Just indicate which part is playing using the appropriate number.
In some cases, like in m. 52, you indicate which part plays what even when there are only 2 parts in the stave and two notes are being played. You should omit the parts' numbers altogether as it's understood which part plays what.
Which brings me to another point. Even on the instrument short names, it's good practice to indicate which parts are assigned to the stave. See below as an example.
Don't use dangling hairpins/cresc./decresc. Make sure to put a dynamic at the end of each one, unless you use a descriptor word like molto cresc. or poco cresc. You can get away with that, even though it's still not a bad idea to punctuate it with a dynamic marking.
Rapid notes in percussion (timpani rolls, triangle rolls, etc.) are now indicated with tremolos and not with trills.
Well, I think that's enough for now. Remember, these are just tips to help make your score more user friendly. As far as I know, there isn't an MLA format (so to speak) for score arranging, so I would evaluate each of these on a common sense basis to see if they truly work for you and what you're going for.