Get onto
https://www.mig-welding.co.uk/The videos are worth looking at, but the forum is invaluable. I taught myself MIG by basically welding off-cuts, posting a bunch of pictures, applying the feedback and doing it again. They have TIG, ARC and other sections too.
Buying the kit and learning to TIG is expensive. The better the machine, the easier it is to learn, and the less gas you will waste, but the up-front outlay is much greater. If you are only needing to stick the odd bit of metal together now and again, it might be worth just finding a local engineering/machine shop that can do it for you for the price of a few beers. Also, it's worth considering what it s that you want to join. Aluminium needs an AC TIG, and even the cheap Chinese eBay machines are £3-400 - one from a reputable inexpensive brand like R-Tec is close to £1000. On the other hand, mild steel can be done with DC, and those machines are much cheaper (avoid scratch start ones that are glorified ARC units - get lift start or ideally HF start). The other variable is the thickness of the material - if it's thick then you will run into power issues and likely need a dedicated supply, but you can do this with ARC or MIG/TIG with multiple passes. If it's really thin stuff (less than 1mm thick) then ARC is going to be really hard, and you will need fine control on the settings for TIG and MIG. TIG with a foot pedal and all sorts of pulse settings can weld really thin stuff, but you need a fancy machine (or years of experience).
As well as a machine, for MIG or TIG you will need welding gas (CO2 or Argoshield for MIG, Argon for TIG). Don't buy the tiny bottles - they run out in no time. Some people use pub CO2 bottles with MIG, but that relies on having a good relationship with your local pub. The most cost efficient way of getting hold of proper welding gas for a hobbyist in the UK is to buy "rent free" full size bottles and then get them refilled when you run out - I don't know if that's possible in Holland. You also need a regulator (to specify how much gas you are flowing), some gauntlets (cheap) various consumables (wire, tips, shrouds, tungstens or whatever) and a mask. Whatever sort of welding you choose, get a good auto-darkening mask - these make life so much easier, especially when learning.
The other thing to consider is where you are going to do this. Do you have a garage or a workshop where you can store all the kit including gas bottles, practise and do the welding itself? MIG and ARC are quite splattery so can spit sparks around the place, TIG is a lot cleaner and quieter. Doing TIG or MIG outside has issues because the gas can blow away (and gasless MIG is a PITA).