Guild Wars 2

I don’t need the lower tiers of crafting materials anymore? Like all I need are the highest tiers to make the legendaries?

If you’re referring to gathering, you’re much better off still picking up what you find.
Reason being that you’re not going to get all of the materials for a legendary on your own. You will buy much of it from the TP. Picking up everything, even when its not related to your legendary, gets you money from the TP to spend on the stuff you do need.

Also keep in mind that the lesser materials are easier to find and farm, are cheaper from the Trading Post, and can be used for transmuting into a higher tier material with the Mystic Forge.

http://wiki.guildwars2.com/wiki/Mystic_Forge#Rare_Crafting_Material_Promotion

The requirements for legendaries are varied; some require only top-end materials, others require T3-6 materials.

In general, you don’t need the lower end materials, but that doesn’t mean that the earlier materials are worthless; like all things there is a market for them, and they can come in handy when working on daily/monthly tasks, gearing up alts, exploiting a gap in the current market, etc.