aero, I've done some research, trying to figure out what would be needed for a basic medicine kit. I checked the finch aviary site, and was struck by some points she made. She has access to a good avian vet. Not everyone has access to an avian vet, and even some of those are not that familiar with treating finches, as they mostly treat the larger (more expensive) hookbills. It can also get very expensive to use a vet.
One problem with finches is that they hide illness very well. Often, by the time you realize the bird is sick, it is so far gone that it is difficult to save it. The other problem is that many illnesses have similar symptoms, yet require different treatments. Giving the wrong treatment is wasting time and money, and putting the bird at further risk.
The other point she brought up is that it is difficult if not impossible to diagnose over the internet. Most people have trouble diagnosing illness in their own birds, much less one they can't even see. And the majority of us on forums haven't had enough experience with specific diseases to be able to recognize and know how to treat them.
Having said that, I do keep a few items on hand, just in case. I haven't used them, as I hesitate to use antibiotics without knowing what I am treating, but I get a small measure of comfort knowing I have them available. These should be purchased in the smallest size available. The ones I have purchased that had a 'use by' date were good for about 2-3 years. There are many brands out there, these are just a start.
Protozoal infections - Ronex, Ronsivet
Bacterial infections - Amoxitex, Amtyl
Coccidiosis - Acox, Cocci-care
Yeast infections - Medistatin
If you use the above medicines, you need to follow up with a Probiotic, or you could have a yeast infection problem.
The following items I do consider necessary, and worth having on hand:
Air sac mites, scaley face - Scatt for a small number of birds
Air sac mites, scaley face - Iverlux, Ivermectin for large numbers of birds
Worms - Wormout or Wormaway
External mites - Avian Insect Liquidator, Pestex
One of the best 'medicines' you can keep on hand is a small hospital cage, just a small cage where you can isolate a sick bird and provide it with some kind of extra heat. Warmth, quiet, and privacy can work wonders sometimes.
Supplements have been covered in many threads on the forum, and there are literally dozens of them out there. In my honest opinion, given that you do not have the easy access to supplies that we have here in the USA, I would concentrate on supplying really good nutrition to your birds. With the right diet, you may find that you don't need all the extras. You also have to consider what birds you are trying to keep. Zebras are very hardy little birds and don't really need all the extra pampering. Gouldians need kelp (powdered or liquid), iodine, or both. They also could use a molting supplement. A small bottle of liquid calcium can help an eggbound hen. Other than that, a good general vitamin should do it.
If you keep finches, you will lose them from time to time, if for no other reason than old age--they don't live long like parrots. Most of the time, when you lose a finch, you don't have a clue as to what went wrong. It is something you just have to accept.
Sorry for the long post, brevity is not my strong suit!
or mites 
. Now the rest of my flock seems to be getting better. Around here I found that there's only dog/cat/poultry medicine all over the place 
. Nothing specific for finches 
or birds.
. but the zebs enjoy water though. I guess I'll take liquid iodine, may be two 8oz bottles. is that too much or too expensive and will it last a more than a year?
? 
. My new LGs need Iodine. I must get that as soon as possible.