Hi Islansoul,

I have been working with MIDI for about 30 years now. Thus the advice that I will give is based on my experiences as well as cost. Since you didn't specify what your limits are I will cover the good to excellent sound sources and equipment needed to make MIDI sound realistic. You will also need to listen to the instrument you want to emulate , pick up the nuances of that instrument then find the MIDI control called a CC number that best adds that nuance.

1-Horns and wind instruments: to get realistic sounding monophonic wind instruments you will need one of the following, a wind controller, a breath controller or software that uses the mod wheel for volume. I use an Akai USB wind controller but for you that means learning another instrument.

In your situation I would use a breath controller like this

http://www.ebay.com/itm/MRTaudio-Breath-Controller-Complete-Set-Compatible-yamaha-BC-Series-V2-/131575713438?rmvSB=true

or a program that uses the mod wheel (CC1) for volume. Garritan's programs are the best bet here.

If your keyboard does not have a 5 pin MIDI in then you will need a 5 pin to USB adapter like this

https://www.amazon.com/YCS-Basics-male-adapter-cable/dp/B00JGZZCOO/ref=sr_1_1?ie=UTF8&qid=1476495135&sr=8-1&keywords=5+pin+midi+to+usb

2- Any instrument that does not have pitch bends or vibrato will sound good with MIDI with little input. These include piano, bells, vibes, drums, organs etc.

As Noel indicated the best MIDI programs cost the most money. If there is a low cost ceiling then Garritan's programs are a great start. I have both the Jazz & Big Band and the Personal Orchestra from Garritan and they are great programs, as is Miroslav Philharmonik and Dimension Pro.

The better all encompassing programs include Kontakt, SampleTank 3, and others. I have Kontakt and it is my go to program for sounds however it is expensive plus I have purchased a lot of third party patches for it. Others here have more experience with SampleTank 3 which is also on the expensive side. Both of these programs go on sale periodically so keep watching for that.

The best sounding but also more costly are the individual programs. Samplemodeling has the best sax and other wind instruments. I have the sax one and it is the most realistic sounding sax emulation that I have ever heard. I also have East West's Symphonic Chorus. I would stay away from East West's programs until you have a working knowledge of MIDI. Their Play, the program needed to run their programs, is a PITA.

To summarize sounds I would go like this:
First to purchase -Garritan Personal Orchestra and/or Jazz & Big Band, Miroslav Philharmonik, or Dimension Pro. Note I do not know if Dimension Pro is available for a Mac.

Next and all encompassing program like Kontakt or SampleTank

Then finally after you have some MIDI experience some individual programs like I listed above.

I hope this helps and if you need anymore info or help feel free to ask.

I want my last spoken words to be "I hid a million dollars under the........................"

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware