1. You need a large box of new DS DD floppy disks. The reason I say "new" is because if you have 30 year old floppies laying around there is absolutely no reason to expect that they still work.
2. Download Workbench 1.3 for your 1.2 machine. Download Workbench 2.0 (or maybe 2.1) for your 2.0 machine. They are all over the internet.
3. Figure out how u will get the disk images onto your Amiga.
You have 3 main options:
3.A: DL on your pc and copy them over to your Amiga using a lame crappy super slow-motion null-modem (serial) cable.
3.B: DL on your pc and copy them over to your Amiga using an elite highspeed parnet (parallel) cable.
3.C: DL the images directly with your A500. You will want to use a terminal program such as JR-COMM and access an internet "Amiga BBS" to do this. Telnet BBS's are massively lower bandwidth than the WWW. You can forget about real web browsing on a lowly A500.
I just now realized that 3A/B/C won't actually work for you until you have your first couple of floppies so u can at least boot up your machines. Doh!
So to get u started I would say find a nice person in your country to mail you the basic floppies to get u started.
Once you have Workbench Disks, Parnet, and some kind of Terminal Modem program then things will get much much easier for you.
At that point u will need to buy 2,000 blank floppies so u can play a few of the best videogames ever created by an Earth-based civilization. Many games take 2-4 floppies each.
There are over 10,000 Amiga games. You won't live long enuff to play them all. So u will just have to pick the cream of the crop.
Good luck!