For starts I suggest purchasing a 9ft Tapered Nylon Leaders ending in around 8lb. Looped ends are helpful.
MikeFish on trademe sells Double X brand leaders for $4 each which is good value. I have used them and they are fine. If you buy from him buy them in 3X size.
Next is the tippit material. During early season when the water levels are high and the fish are greedy and confident I fish with 3X tippit which is around 7.2lb, when the water level drops and the fish become wary I would use 4X, 5X and maybe even 6X…. Often the smaller the fly you choice to use the smaller the leader. To fish a small dry fly probably would require a 5X or 6X tippit. I would personally use Nylon.
At this time of year to the end of the 9ft leader I would tie 1-2ft of 3X tippit, then to that 1-2ft of 5X tippit.
When you get more experienced you could consider changing to Flourocarbon leaders and tippits. They are more expensive, sink slightly faster and maybe less visibile for fish. I have not noticed a difference.
There is also PolyLeaders but they are for more specialised presentations. It is possible to use a 5ft floating Polyleader insterad of a 9ft tapered leader….