For me Rune essence is almost impossible to get, I can get pure essence fast, but not rune essence, and I need rune essence to craft at world 16.

 

Any tips how to get like 3k rune ess quicky?

Buy it on F2P worlds. A a member you will not be able to mine 3k of it, nor will you want to wait for 3k worth to be dropped!

It's hard to buy for 30ea nowadays, you may have to go higher, like to 40 each. For just 3k of it, that shouldn't be that big of a problem. Otherwise, try world hopping in all f2p worlds between 1 and 11, check both Varrock banks.

You can always mine 1k pure ess, sell it (100-120ea last time I checked, might be different, though) and buy the 3k rune ess with that money.