Last edited by aidy; 03-24-16 at 02:17 PM.
If you're in Belgium check out Decathlon for cheap sleeping bags and tents. My girlfriend and I bought the T3 Ultralight last year and it's served us well over several trips bike and car camping. Last summer they had a deal on the T2 (2 man, 2kg) + sleeping bag (800g) + self inflating sleeping mat.
No stealth camping on the main land for me I'm afraid, only in the UK, which is even denser populated in most parts. I've got on ok.
I'd say get a job and save up a few hundred more euros so you can at least no have to worry about eating. A couple of weeks agency work will get you plenty.
"Public restrooms" are the least of your problems.
Your bike sounds like it will either by in a rustic sort of way, or totally suck.
You know more about how much it will cost to feed you than we do. I got by in france once on baguette, camembert and tomatoes. You'll probably want the odd hot meal though. If you're eating noodles, you're carrying a stove, fuel and water.
Stealth camping is easy. Find a spot just before dusk, wait till dark, camp. The biggest problem is you may not get a full night's sleep every night. Take decent maps and you should always be able to find a state/national/municipal park. Camping generally prohibited, but who'll know? Now that I think about it, I've done this in Karlovy Vary (turned out to be a public park - woken up by joggers and school kids playing soccer!) and Adrspach-Tplesky national park in Czech Republic.
Your biggest problem to me sounds like lack of money. €150 is very little, even if everything goes according to plan. At the very least you should borrow some emergency funds for food, bike parts, train back etc.