Hi!

I am dutch (I lived in Roterdam) so I know quite a lot about touring in my lovely flat little country :-)

The cycleroads in Holland are exellent so a simple cheap bike should be OK. In Belgium the roads are a little more rough but still a normal bike should do fine.
The Ardennes in the east of Belgium and Limburg in the south east of Holland are quite hilly so if you plan to bike there you'll need 21 gears. For the rest of Holland and Belgium 3 to 12 gears should be enough.

The cheapest way is to buy a simple (second hand) touring bike
(28' tires) and fit it with a front rack and a backrack. Best would be steel racks as these are stronger than alluminium ones. The backrack should be able to carry 20kg.
A bottlleholder for on the frame is also useful as is a backmirror. Especially if you want to cycle in Amsterdam on a loaded bike
If you want to use a MTB (not neseccary in Holland and Belgium) buy one without rear suspension as this won't work with heavy loads.

For tires I would recommend Schwalbe Marathon tour. They are not the cheapest but they will save you a lot of flat tires

Panniers should be watertight (holland=rain ) . Most of us use either Vaude or Ortlieb but these are quite expensive. You can also buy cheep canvas ones and store your gear in large garbagebags.

The rest of the gear you can best lend from friends or buy on e-bay.
The most expensive thing is the tent followed by the sleeping back. The sleeping back should be comfy to 8 degrees when camping in spring or summer so a simple one would do.

For cooking I would recommend Camping Gaz gear as you can buy cannisters on every camping in Belgium and Holland and they are cheap and easy to use.

For clothing: don't forget to bring a rain jacket and trousers with you and a warm pullover (fleece). Preferably don't wear any cotton clothing as it will get wet quickly and dries slowly. Synthetics or wool are better. In Germany and perhaps also in Madrid you can buy cheap cycle clothing at certain supermarkets or in internet shops, so just take a look there. For a tour like yours you don't need expensive clothing.

When you are a student (like me) there are always loads of old unused bikes standing around the campus. Practise your repairing skills on those old crappy forgotten bikes

Most common bikeproblems:
How do I fix a flat tire
How do I remove my wheel
How do I change my brakepads and adjust my brake
How do I cange my chain
How do I adjust my derailleur
How do I replace a broken spoke

If you have more questions just mail me

Cycle the world,
Marc