Reddit reviews One Hundred Studies for Trumpet: Schirmer Library of Classics Volume 1928 Trumpet Method

Like /u/MarioKartGuy27 said, the most important part of becoming a better sight reader is to practice sight reading every day. The "Famous Melodies" in the back of the Arban are a good starting point. Another good book is Sachse's 100 Studies, or maybe try some books by Sigmund Hering.

Here are a few more tips that will really help your sight reading:

• Sight reading is mostly just pattern recognition. Learn all your major scales, then all your minor scales, then all your major and minor arpeggios, then dominant 7th arpeggios, then diminished 7th arpeggios (these are all in the Arban). If you can play these with ease, most music will seem much easier to sight read, because a shocking amount of music is just different versions of these patterns strung together.
  
• Start practicing transposition - the Sachse linked above is a really good book for this. A nice approach for Sachse is to play one study a week, transposing to one or two new keys each day. It will be painful at first but just go slowly and it will get better in time. Nobody was born knowing how to transpose, we all had to practice it.
  
• Finally, deliberately train yourself to read a few notes ahead at a time. Etudes (which usually have the same rhythm over and over) are good practice for this. Try "seeing" the notes in groups of two, then three, then four.