If you're truly starting out from scratch, i.e. not even having camping equipment or transport, it's probably best to really look for people with who you can tag along. Engage in social activities in your climbing gym, make friends there, ask if they'd ever like to go /out/. Alternatively, look around in the Randstad for non-student climbing associates that focus on (outdoor) climbing trips. There have to one or two at least.>buying camping equipment might be too expensive
Another piece of advice that's really crucial is that outdoor equipment doesn't have to crazy expensive. Forget the discussions like this >>1669871
where the total equipment cost may be up to ~1000-2000 euros - cheap stuff from Decathlon will suffice for your purposes. There, a cheap winter puffy may be 20-40 euros, while a Patagonia brand may be 200 euros.
Get a list of dream equipment (I want a Vaude Taurus 2P ultra light tent, but that's 500 euros..., a 450 euro Arc'Teryx rain hardshell), then look for material that achieves (part) of the same purpose at a more reasonable price point. >What would be the best way to go about making a weekend trip to Germany or Belgium?
Logistics wise, for Belgium, a couple of climbing crags have huts you can sleep in during peak season, managed by local climbing associations. These are usually fairly bare, but warm and cheap. Alternatively, you can just hike into the forest and camp there – usually, if you don't make noise, don’t make a fire and clean up your camping spot, people don’t mind. For Germany, I usually just find cheap campings around the boulder crag.
Travel wise, going by train to the Ardennen is possible, but it’s neither cheap nor fast. If you decide to do so, just go for three days instead of two. I have only gone to Germany by car, so can’t give you any advice there.