Looking for some help with my garden design. This is in the middle of an industrial estate to provide a space people can get away from all the concrete and grey. The ground is concrete and will need some levelling but the intention is to build 71m of mostly continuous planters to separate from the concrete.

Planters will be around 90cm high 90cm wide with bushes and small trees.

Im looking for advice for affordable solutions to build the planters from and what type of soil to fill them with?

Wood will be your cheapest option but what kind of wood you use will make a difference in how long they last and hold up to the elements. Regular treated pine is the cheapest and you can stain or paint it after a few months to the color you want. You will just need to do that every few years to keep it looking good. Line inside with landscape fabric to keep the soil directly off the wood.

Plants. That is one question that will be hard to answer without knowing where the project is located. Just the city is good enough on here.

It depends on you access, doesn't it? If there are lots of bricks (very nice to build with and look at) or cinder blocks (easy to build; needs help visually) left over from the building project, you could use them. Ditto lumber and corrugated metal sheeting. Cinder block is durable and low-maintenance, but bulky. Metal sheet on a frame of steel pipes or wooden 2x4's gives the most interior space per square footage. If properly rust-proofed, it lasts longer than wood, but is less attractive. OTH, it can be painted a cheerful colour, which might change every three years. Cedar is inexpensive, attractive and quite durable. Personally, I'm partial to cedar slab, which is readily available and very cheap where I live (waste product of a Mennonite sawmill). A little harder to work with, as the boards are irregular in width and thickness, but the very randomness of it has a certain charm that factory-precise boards lack.