Pioneering poles will last much longer if they are stripped of bark before use. Try to source spruce, larch or ash, and avoid brittle woods like willow and poplar. For younger sections or activity inside you can use spaghetti (with marsh mallows), pea sticks, bamboo canes or Scout staves.
Use good quality rope such as 8 or 10mm diameter sisal for lashings that will take a strain, though thinner sisal can be used for small pioneering projects. Remember that natural fibre sisal will tighten when wet but equally slacken once dried. This may affect the integrity of your structure. String or elastic bands works well with cane structures indoors.
Some structures may need stabilising using guy ropes.
You may need these to anchor guys or to lash the end of the structure to the floor.
to knock pegs or pickets in to the ground
Pickets (long peg/post)
For anchoring rope supporting the structure (especially bridges or runways)
Blocks / pulleys
A large hand drill to make a hole in the ground to make upright spars more stable.