You won\'t get far with $100 for a library!
There are a lot of cheap percussion and loop libraries, but realy no good (or none at all) orchestral libraries.
A standard, not too expensive orchestral percussion library would be the Percussion & Harp disc of Siedlaczek\'s Advanved Orchestra series, but this cd alone still is around $225. But it\'s worth a try.
Search for this library at http://www.soundsonline.com
For a cheap brass library you should consider the X-Sample series, which has a lot of solo brass instruments. Take a look at http://www.x-sample.de
The best Orchestral percussion library by far is the Ultimate Percussion library at $299. Definitely worth every penny!! Xsample brass disk would be the cheapest at about $130 for starters. You may be disappointed with the trumpet though as it does not excel in the upper ranges.
Don\'t know if you checked, but Worra\'s Place has a lot of free gigs. The quality varies, but they are free.
Mail me at email@example.com and I can help you check the gigs since not all are published right now.