general tip

Look up what you want (directionally) in amazon, evaluate the ratings, then search for the company that sells those things, and go to their website. They often offer much cheaper prices than on amazon! look for coupons every time you buy something at these stores. And you can also ask for "Angebote" if you buy a lot, so they send you an offer that is often even cheaper!

where to find what for best value/money

Write here in English and German where you can find good value for money
Afterwards, we'll be able to just search in loomio if we want something and find the best supplier :D
- ratchet straps/spanngurte: https://www.mcs-cargosecurity.com
- zip ties/kabelbinder: https://powerpreis24.de/100-Stueck-Kabelbinder-schwarz-48x-360mm
- rope/seil: https://kanirope.de/polyesterseil-polybraid-kanirope-4mm-500m-spule-weiss-8-fach-geflochten or the natural version: https://www.ebay.de/itm/vidaXL-Seil-100-Jute-6-mm-500-m-Naturhanf-Hanfseil-Tauwerk-Juteseil-Tau-Seil/401507587014
- generator rental/Aggregate mieten: Boels.com
- abbsperrband/perimeter tape: https://www.idealo.de/preisvergleich/OffersOfProduct/393165_-absperrband-rot-weiss-500-m-81-83-30-promat.html
- wood: there is a lot of free wood in Berlin! Sometimes it comes wired shapes like beds, tables, closets or trees (and even pallets!) but if you have a place to store and a car you can get A LOT of wood for building i.e. https://www.ebay-kleinanzeigen.de/s-berlin/sortierung:preis/anbieter:privat/holz/k0l3331